Method and apparatus for using monochrome images to form a color image

ABSTRACT

A permanent color record of an image provided by a scanner employed in medical diagnostic procedures is formed on a standard sheet of 8×10 inch black-and-white film by three separate monochromatic record images of respectively different ones of three color components of the scanner developed image. The film sheet with its three black-and-white images is viewed on the screen of a viewer having three lenses positioned to project light of three different colors in converging paths through respective ones of the monochromatic record images and to project three image components in mutual superposition on the viewer screen. The three different color image components on the viewer screen are precisely positioned so that there is no visibly discernible misregistration. Either the three image components on the color record are formed on the sheet film with a predetermined maximum misregistration or the viewing system is adjusted to accomplish such maximum misregistration on the viewer screen.

This invention was made with Government support under Grant No.1-R43-CA52314-01A1 awarded by the National Institutes of Health. TheGovernment has certain rights in the invention.

FIELD OF THE INVENTION

The present invention relates to medical diagnostic imaging and moreparticularly concerns methods and apparatus for making and displayingmulti-color record images.

BACKGROUND OF THE INVENTION

In common radiology clinical environments the diagnostic radiologistseldom sees the patient in person. Examination procedures are performedby trained and qualified radiology technicians, or, in the case ofultrasound imaging, by sonographers. Examination results arecommunicated to the radiologist diagnostician by means of rapid accesshard copy images on film. The film images are interpreted or read bybeing placed on a light box. The system is quick and cost-effective andconserves scarce resources since it allows both the radiologist and thediagnostician to work with increased efficiency. For such system it isobvious that quickly available hard copies of a very high image qualityand high stability are critical.

For information which is presented in black-and-white or gray-scaleform, technology to record and view diagnostic films has been highlydeveloped over the years. The common x-ray film system is an example.Film image quality can be very good, having high spatial resolution anda wide gray scale. Access to the permanent record is quick, becausedeveloped and dry film images can be delivered within about two minutesafter an examination is performed. The film is archivally permanent andcost is low.

In the last few years, however, there has been an increasing use ofcolor in diagnostic images. In some imaging modalities color in theimages serves to emphasize selected details or features, such as byusing certain colors to designate densities or density gradients beyondpreselected thresholds. This adds no new information but facilitatesinterpretation of information already contained in the image. However,in other areas, such as, for example, in diagnostic ultrasound, color isused to present new information which is not available in theblack-and-white gray-scale image. This is done, for example, incolor-flow or color-doppler images, wherein information about directionand velocity of blood flow is presented by color coded patchessuperimposed on the gray scale image everywhere the ultrasound sliceintersects a blood vessel. The color-doppler imaging technique isgaining wide acceptance in certain diagnostic procedures.

However, hard copy color images are more time-consuming for developmentand delivery, and are more expensive and less convenient. Hard copycolor images are not as archivally stable and often are not viewable bytransmitted light, nor do they always provide true diagnostic imagequality. There are of course a number of known methods for obtainingcolor images, but none has the combination of advantages provided bycommonly used black-and-white film.

In conventional color transparency systems a silver halide photographicfilm, for example, a so called integral tri-pack of three layered lightsensitive emulsions is used, where each layer is sensitive to oneprimary color. During exposure three color records are made as latentimages in the three layers. During chemical processing after exposurethe latent images are developed as silver images and then converted todye images in the complementary colors. In this technique, as in mostother color systems, the complete color pictorial image in viewable formis assembled on the material which forms the permanent record media.

Another example of color printing is thermal dye transfer. In thisprocess three subtractive primary color dyes, each coated on its ownpiece of substrate, are successively brought into contact with areceiving substrate and the dyes are selectively transferred bysublimation, activated by a thermal scanning head which passes over theline of contact between the dye and the receiving substrate. After threepasses the result again is a complete color pictorial image in viewableform assembled on the material which is the permanent record medium.

Yet another example of a color printing technique is thenon-photographic use of ink jet printing. In this process multiple jetsof variously colored ink are selectively squirted onto a substrate as itpasses by. The result again is a complete color pictorial image inviewable form assembled on the material which is the record medium.

All of the known color hard copy systems employ separate color channelsthat are combined into a color image on the hard copy material itself.In the prior art the color image itself becomes the permanent pictorialrecord, with all of the inherent disadvantages of a permanent colorrecord. The black-and-white record provides higher resolution, bettergray scale capability, better temporal stability, and simpler andquicker film processing and handling by widely available standardequipment.

Thus it will be seen that the conventional black-and-white photography,which has long been a standard in the industry, has the many advantagesof being quick, cheap, convenient, archivally stable, viewable bytransmitted light and having high diagnostic image quality. In addition,the widespread and long-term use of black-and-white imaging has made thetechnique and the required processing equipment and its use well knownand widely available. However, as mentioned above, the black-and-whitetechnique lacks the ability to contain certain information that can beincluded in a multi-color image. Multi-color image techniques previouslyavailable, on the other hand, although capable of containing theadditional information, lack the many advantages of the standardblack-and-white processes.

Accordingly, it is an object of the present invention to provide amulti-color record that is readily viewable while avoiding or minimizingproblems of prior art imaging systems.

SUMMARY OF THE INVENTION

In carrying out principles of the present invention in accordance with apreferred embodiment thereof multi-color monochromatic color imagecomponent signals, collectively representing a color image of an object,are employed to produce on a common piece of monochromatic film mutuallyseparated monochromatic record image components of respective ones ofthe color component signals with a predetermined nominal relativepositioning. The separated monochromatic image components are viewedthrough a multiple path optical system that simultaneously projects theseparate monochromatic record image components in precise superpositionon a screen, each of the projected image components being illuminatedwith a different colored light. According to a feature of the inventionthe color record image components are positioned on the record film witha maximum deviation from a nominal positioning that is not greater thana deviation that would cause a visibly discernible misregistration ofthe color components when the monochromatic images are displayed inmutual superposition upon the screen of the viewer. According to anotherfeature of the invention, lack of precision relative positioning of themonochromatic record image components on the record film is accommodatedin the viewer by adjusting the optical paths of the viewer, eithermanually or automatically, until registration of the projected imagecomponents on the viewer screen causes no visibly discerniblemisregistration of the color components.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a simplified showing of an overall camera and viewer system;

FIG. 2 is a functional block diagram of a camera employed to make apermanent color film record on monochromatic film;

FIG. 3 illustrates relative positioning of record image components andviewing screen of a viewer;

FIGS. 4 and 5 illustrate physical layout of an exemplary camera;

FIGS. 6 and 7 illustrate physical layout of an exemplary viewer;

FIGS. 8 and 9 show different views of a film holder drawer of theviewer;

FIGS. 10 and 11 schematically illustrate manual lens adjustment of theviewer;

FIG. 12 illustrates a film record having color images and automaticconvergence adjusting spots;

FIGS. 13 and 14 illustrate front and side views of the physical layoutof portions of a viewer having automatic convergence adjustment;

FIG. 15 is a functional block diagram of operation of the automaticconvergence adjustment of FIGS. 13 and 14;

FIG. 16 is a flow chart of a program for the automatic convergenceadjustment;

FIG. 17 illustrates a camera arrangement in which a conventional camerais provided with an adapter to form a color record on black-and-whitefilm;

FIG. 18 (sheet 11) shows an alternative film record image componentarrangement;

FIGS. 19 and 20 show portions of a modified viewer with movable lenses;

FIG. 21 (sheet 10) illustrates staggered positioning of film recordimage components;

FIG. 22 shows an arrangement for reversing deflection directions of theCRT;

FIGS. 23-26 illustrate modified arrangements and orientations of filmrecord image components; and

FIG. 27 shows arrangement of lenses of a modified viewer for use withfilm records of FIGS. 23-26.

DETAILED DESCRIPTION OF THE INVENTION General System

FIG. 1 is a simplified illustration of components of a system employingprinciples of the present invention for making and viewing a colorrecord for medical diagnostic purposes. A conventional scanner 10, suchas an ultrasound scanning device, which may be an Acuson Model 128 madeby Acuson, or an ATL Model Ultramark 9 made by Advanced TechnologyLaboratories, provides an output signal on lines generally indicated at12 in the form of three separate color component signals of an image ofa patient being scanned. Frequently the scanner output will, inaddition, provide a sync signal together with the three color componentsignals. When the operator desires to record an image, the scanneroutput signals are fed to a camera or record forming device 14 whichtemporarily stores the signals from the scanner and sends the colorcomponent signals one at a time to a monochrome cathode ray tube (CRT)(not shown in FIG. 1) contained within the camera. The face of the CRTis sequentially exposed through a camera lens and shutter systemarranged to form a separate monochromatic image on a sheet of film 16 ofeach of the individual color component signals. The camera is arrangedto employ standard sheet film, such as a standard 8×10 inchblack-and-white video image recording film sheet. In a presentlypreferred arrangement, such film will provide permanent records of twodifferent color images. Each permanent record image comprises threeseparate monochromatic image components. Thus, for a first image, thefilm record includes monochromatic record image components 18,20 and 22,which, as a set, collectively define a first multi-color image. The samefilm sheet also may contain a second set of monochromatic record imagecomponents 24,26, and 28 collectively defining a second multi-colorimage. Thus, for example, on the film record 16, monochromatic orblack-and-white image component 18 represents the red color component ofa color image, monochromatic image 20 represents the green component ofsuch color image and monochromatic image 22 represents the bluecomponent of the color image. Similarly, monochromatic images 24, 26,and 28 represent red, green and blue image components of a second colorimage provided from the scanner. Accordingly, as illustrated, thestandard sheet film has two sets of image components, with each setcollectively defining a different color image.

The standard monochromatic sheet film 16, after exposure in camera 14,is processed in a conventional manner to provide permanent transparentmonochromatic record images on standard black-and-white film, with threeimage components collectively defining one full color image. Thedeveloped record film 16 is then inserted in a viewer 30, which isprovided with three separate optical paths having light of differentspectral content transmitted along each path. The three optical pathsconverge on a viewer screen and each passes through a different one ofthe transparent monochromatic record image components 18, 20 and 22, forexample. Individually colored converging light beams passing through thetransparent monochromatic record image components 18, 20 and 22 arepositioned by the lens system of the viewer so that all three projectedimages are superimposed on the viewer screen with a misregistrationbetween any two of the projected images that is not greater than theamount that would cause such misregistration to be visible to the viewerin the form of color fringes or the like.

The system may be employed with a standard silver halide basedphotographic film system and thus use conventional black-and-whiterecording film, of the kind that is currently used to make gray scalediagnostic images. The camera can record either color (multiplemonochromatic color image components) or conventional black-and-whiteimages. Thus, the system exhibits a number of advantages, some of whichare described in the following paragraphs.

Either color or black-and-white images may be recorded on conventionalblack-and-white film by the same camera. Separate cameras are not neededfor black-and-white and color imaging. Physical size and powerconsumption allow the described camera to fit in space allocated in anultrasound cart for current black-and-white cameras.

Film can be processed in conventional black-and-white film processorswhich are already present in most radiology departments. There are nospecial processing requirements, and film can be available for viewingin one to two minutes after exposure.

Image quality of both color images and black-and-white images is as goodas that of current black-and-white images produced by conventionalcameras because the film is the same. Gray-scale range and spatialresolution are just as good for the color images of the present systemas that which radiologists are accustomed to in current black-and-whitefilm images. Further, any image quality improvement that may be made inblack-and-white film systems will enhance the quality of the colorimages as well.

The recorded black-and-white film images of color components havearchival permanence which is the same as that of current black-and-whitefilm. Filing and storage of such film can be integrated into the samesystems as used for current black-and-white film. The use of the currentcommon black-and-white film is economical because it is so widely usedat present. The economy of this film is inherent in its structure, whichconsists of a single emulsion layer coated on a single substrate, unlikecolor media which require multiple layers, complex chemicalcompositions, complicated and critical processing and/or auxiliarymaterials to produce the colors. No current system for producing colorimages for diagnostic imaging applications has all of these advantages.

As will be described below, the present system can also be used withnon-silver films, such as in systems which use electrophotographic,thermographic or the Polaroid Helios imaging techniques. In sucharrangements corresponding advantages will apply because the techniquesemployed for the system illustrated in FIG. 1 will be used for recordingof black-and-white or color images.

Camera

FIG. 2 shows a block diagram of components of the camera 14 of FIG. 1.Also illustrated in FIG. 2 is a conventional scanner, such as anultrasound scanner that provides inputs to the camera. Conventionalscanner 10 provides outputs on lines 36,38 and 40 in analog formrepresenting color components red, green and blue, for example, of animage processed by the scanner. These signals, together with a syncsignal (not shown) which may also be provided by the scanner, are fed toan analog-to-digital convertor 44, which may be part of the camera, thatprovides digitized versions of the red, green and blue signals to aframe memory 46 of the camera. One frame of each of the red, green andblue color components is stored in the frame memory. The individualcolor components (R, G and B) are fed from the memory 46 to amultiplexer 48 which sequentially feeds the digitized color componentsto the Z axis control of a cathode ray tube 50, which may be, forexample, a standard monochrome high resolution, flat face, seven-inchCRT, such as the Clinton CE678M7P45. The display on the face of thecathode ray tube 50 is fed through two sets of lenses, generallyindicated at 54 (there being three lenses in each set), with each lensbeing controlled by an individual shutter, generally indicated at 56.Each lens is arranged to project the image from the entire face of theCRT to a different predetermined area on the conventional monochromefilm sheet 58. For any one image, three lenses, such as lenses 60, 62and 64, are provided, each having its own individually controlledshutter 66, 68 and 70, respectively. The lenses are arranged in an offaxis configuration so that lens 60, for example, will transmit the redcolor component to image component area 18 on the film sheet 58, withthe lens 62 transmitting the green component, for example, to the imagearea 20, and the lens 64 transmitting the blue component to the imagearea 22 on the film. The camera employs no color filters.

A controller 76 is provided that may be initiated by an operator'scommand provided at a terminal 78. The controller includes anappropriately programmed microprocessor that provides control signalsfor the various components of the system, including a synchronizingsignal on a line 80 to the analog to digital converter, a signal on aline 82 to the frame memory for extraction of information from thememory, a signal on a line 84 for control of the multiplexer, a blankingcontrol signal on line 86 to the CRT for control of Z axis blanking, andshutter control signals on six lines collectively indicated at 90 forselective individual operation of the several shutters. It will beunderstood that where the system is arranged to provide recording of twoseparate images, as illustrated in the film 16 of FIG. 1, six separatelenses and six separate shutters are provided in the camera. Thus theset of three lenses 60, 62 and 64 is duplicated by second set of threelenses (see FIG. 4 or 5), with each lens of such additional set alsohaving its own shutter.

If deemed necessary or desirable, an image processor 94 may beinterposed between the output of the multiplexer and the input of thecathode ray tube to improve image quality. For example, a processor mayperform a gamma correction for transfer characteristic distortion tocorrect the image to yield a linear overall curve of film density versusinput signal variation, canceling the nonlinear effects of the transfercharacteristics of the CRT and the film. Alternatively, a predeterminednonlinear overall transfer characteristic can be generated to spread outthe density shades in a particular portion of the density range in orderto facilitate diagnostic interpretation of the final image.

In general, for operation in color mode the multiplexer, the CRTunblanking, and the lens shutters are synchronously gated by thecontroller to produce three monochromatic record images for each of twodifferent color images on the black-and-white film. In black-and-whitemode of the camera, a single one of the color components is selected,the multiplexer is fixed on the selected channel, (the green channel forexample) and CRT unblanking and the shutters are controlled to producesix different complete monochromatic images on the black-and-white film.

The optical arrangement shown in FIG. 2 is one of several which can beused to distribute images from the CRT to the film. For example, the sixseparate lenses used in the camera of FIG. 2 can be replaced by a pairof lenses corresponding to lens 60, for example, which pair is moved tothree different positions, namely the positions corresponding to each ofthe lenses 60, 62 and 64 individually, by means of a linear translationmechanism. Alternatively, a single lens can be moved to six differentpositions by two linear translation mechanisms in an X,Y configuration.Still another alternative is to use two stationary lenses and move thefilm in its cassette to three different positions for the exposure.Still further, some combination of lens motion and film motion can beemployed to produce six separate images on the single sheet of film.

The lenses are employed in an off axis configuration which isillustrated in FIG. 3, together with the six image components and theviewer screen. Thus a first vertically spaced set of lenses, lenses 60,62 and 64, is shown in FIG. 3 horizontally adjacent a second verticallyspaced set of identical lenses 60a, 62a and 64a, all of which areprecisely and fixedly positioned relative to the camera and relative toone another. The lenses form six image components illustrated as imagecomponents 18, 20 and 22 in FIG. 3 for the lenses 60, 62 and 64,respectively, and as image components 18a, 20a and 22a for lenses 60a,62a and 64a, respectively. The images 18, 20, 22 and 18a, 20a and 22aare positioned on a standard 8×10 inch black-and-white film, indicatedin FIG. 3 by the dotted lines 100. Also illustrated in FIG. 3 is theposition of a screen 102 of the viewer 30, as will be more particularlydescribed below. Thus, effectively, the six lenses and six imagecomponents are symmetrically located in off axis positions relative tothe axis of the cathode ray tube. In a typical example for use with an8×10 inch film, each of the film images 18, 20, 22 has a dimension of90×67.5 millimeters, with a vertical center to center displacement of 79millimeters and a horizontal center to center displacement of 97millimeters. Each lens of the upper and lower pairs of lenses 60, 60a,and 64, 64a is displaced vertically from the inner pair of lenses 62,62aby the same 44.011 millimeters, and the two sets of lenses, such as lens64 and 64a, are displaced horizontally by 27.020 millimeters on eitherside of a vertical center line of the film.

In the exemplary embodiment illustrated in FIG. 2, analog video signalsin the commonly designated RGB format representing color images from thediagnostic imaging host equipment, namely scanner 10, are fed into theanalog-to-digital converter of the camera. The video signals come in onthe three lines 36,38,40, each containing information of one primarycolor component of the color image. The signal in each color channel canbe considered to contain a gray scale signal representing luminancevariations of the corresponding color component.

At the initiate command the converter digitizes the next frame of thepicture (all three color components) and places all frame components inthe frame memory 46. A typical amplitude quantization of each colorpixel is 8 bits per color, resulting in 256 shades for each primarycolor and requiring a total of 24 bits for each pixel in the memory.

The frame memory can also be used to insert black borders around theimage components to appear on the film. This is desirable so that lightdoes not shine through the borders when the images are viewed. To thisend, if deemed necessary or desirable, the frame memory 46 may be madesomewhat larger than the image components, and pixels outside of theimage area are set to black or super-black level. Further, for purposesto be described below, the signals fed to the monitor are inverted sothat light and dark portions are interchanged. The entire digitizationof a single video frame must take place in real time, which requires33.4 milliseconds for one frame interval of RS-170 video signals.Digitization of each horizontal scan line must take place in 52.5microseconds, which is the interval for a single active line. However,after the image has been captured in the frame memory the remainder ofthe process in the camera can proceed at a slower pace.

After frame capture, one color component at a time is selected by themultiplexer from the frame memory and sent to the signal processor 94from which serial image information is transmitted to the Z axis controlof the CRT one horizontal line at a time, where it is scanned onto theface of the black-and-white cathode ray tube. The scan rate can berelatively slow, since the scan is not visually observed. For example,one single scan per second for each color component can be employed. Inuse of a slow scan technique, spaces between adjacent horizontal linescan be filled in by repeating the same line several times at a ratewhich overlaps them on the CRT or by generating new intermediate lineswhich are interpolated by the signal processor and sent to the monitorand inserted in their proper places in the signal stream.

The steps in the recording process, as controlled by the controllermicroprocessor, are as follows: Following an initiate command a singlevideo frame is digitized and all three components captured in the framememory as described above. The shutter behind the lens corresponding tothe position o the film for the first image component, which may be redfor example, is opened. A suitable delay of 100 milliseconds, forexample, is provided to allow mechanical vibration of the shutter tocease. Then the multiplexer is operated to select the red component fromthe frame memory and transmit this component to the CRT via the signalprocessor. The CRT is unblanked (it had been previously blanked atinitiation of the process), and the single frame, single componentsignal is fed to the Z axis control of the monitor one line at a time tobe scanned horizontally across the face of the CRT. The CRT is blankedagain. Thereafter the "red" shutter closes completing exposure of thered image component on the film. The "green" shutter openssimultaneously, with a similar delay to allow for damping of shuttervibration. The multiplexer is then operated to select the green framecomponent from the frame memory to feed this through the processor tothe CRT. The latter is then unblanked to allow the green image componentto be scanned on the face of the CRT one horizontal line at a time,after which the CRT is again blanked. The second or green shutter thencloses to complete green image component exposure. Simultaneously thethird or "blue" shutter opens, followed by a suitable delay for damping.The multiplexer now transmits the blue component from the frame memoryto the CRT, which is then unblanked so as to cause the signal to scanacross the monitor face one line at a time, after which the CRT is againblanked and the blue shutter closes, completing blue image componentexposure. All three image components have now been exposed at threemutually separate locations on the film.

During the open period of each shutter the particular one of the siximage areas of the film is exposed to the entire face of the cathode raytube. The time of the CRT unblanking controls the exposure time. Byvarying the scan rate, both horizontally and vertically, exposure timemay be changed. Different exposure times for the different colors may beemployed.

If deemed necessary or desirable, CRT brightness drift may be cancelledby use of a luminance test pattern sensed by a calibrated light sensorin the camera in accordance with well known procedures. Exposure time orbrightness may then be adjusted to compensate for brightness variation.Exposure time in the case of the described camera can be readilycontrolled by changing the rate of a single scan.

For operation of the camera in a black-and-white mode instead of thecolor mode the camera will record one image for each full record to bemade instead of recording three image components, as in the color imageas described above. Preferably, as mentioned above, the black-and-whitevideo image will be provided on the green channel, and the multiplexerfixed to that channel. Single images from the CRT are distributed to thefilm by opening one shutter for each image. The shutter opened is thatwhich is behind the lens corresponding to the position of the filmreserved for the images in sequence. Thus, six different black-and-whiteimages may be recorded in six different positions on the film.

If the scanner 10 should provide a digital rather than an analog outputof three video signal color components, the analog to digital converter44 may be omitted.

The described camera, in another embodiment, may employ no internaldigital video, but will accept analog video in three channel RGB format(or some other format converted to RGB format). Such a multi-componentanalog video signal will be sent by this analog camera one component ata time directly to the CRT Z axis control, with the CRT operating at theinput scan rate and not in the slow scan mode that is employed in thedigital camera described above and illustrated in FIG. 2. The camerawhich accepts the analog signals directly needs no frame memory and nosignal processor. Stored analog video frames can be provided from theinternal frame memory of the host ultrasound scanner. Such an analogcamera is simpler but lacks the digital capability that can improveimages and yield better pictures.

The camera system described above, is arranged to be directly connectedto the host diagnostic imaging scanner. It will be readily understood,however, that the output of the diagnostic scanner may be recorded onsuitable intermediate storage media such as disc or tape. Such disc ortape is then transported to the camera for playback and recording on the8×10 inch permanent film record. In such a configuration a suitableacquisition or image storage unit at the diagnostic scanning machine isarranged to record the selected electronic images so that several ofsuch diagnostic scanners may share a single camera. At the cameralocation a single playback unit is provided to play back theintermediate storage disc or tape and thereby furnish the electricalinput for the camera in place of the signals such as those provided fromscanner 10. Except for the fact that the operation takes place in twoparts, the first part being at the acquisition unit where the image isrecorded, and the second at camera film recording time, the operatingsequence is the same as that previously described.

The camera described herein employs a cathode ray tube having an imageon its face that is photographed on the film. Other types of camerasproducing film images by other means may also be employed. In fact, anytechnique that produces accurately sized images in precisely placedpositions on a transparent medium can be used. For example, in aso-called laser camera, an intensity modulated narrow laser beam isscanned back and forth over the width of a sheet film as the film ismoved. In such an arrangement, because the scan must cover the entirewidth of the film, it is not practical to generate one small image attime in different places, as is performed with the CRT based camera.Instead an electronic representation of the entire set of images to beplaced on the film, including separate images in various places, isassembled in a larger memory and serially sent from that memory to thescanning mechanism to generate the exposure of the entire film.

Still another kind of camera employs an electrophotographic process. Insuch an arrangement a sheet of film coated with a previously chargedtransparent photoconductor is caused to pass by a fiber optic CRT facein very close proximity. The CRT is scanned with a moving raster ontothe photoconductor film as the latter passes, selectively dischargingthe photoconductor. Movement of the film is synchronized with movementof the raster, which is only a few lines high in such an arrangement.Thus, in this arrangement the CRT provides the X scan and the movingfilm provides the Y scan. After the film passes the CRT, it passestoning and fusing stations similar to those in a xerographic photocopierand then emerges with an appropriate record image on it. As in the lasercamera, the entire image to be put on the film is first assembled in alarger memory. In both this arrangement and the laser camera theresulting permanent film record comprises three sets of individualrecord image components.

Another example of alternate recording techniques that may be employedfor forming permanent multiple color image component records is thePolaroid Helios technology, which employs a layer of carbon pigmentedimaging material sandwiched between a substrate and cover film. Theimaging material is exposed by intensity-modulated laser beams which arescanned over the imaging area. After exposure, the cover sheet is peeledoff. Where there is to be a dark part of the image, the pigmentedmaterial adheres to the substrate; where there is to be a transparentpart of the image, the pigmented material comes off with the coversheet, which is discarded. The process is a binary one, yielding areasof either high light transmission or low light transmission. To achieveintermediate shades of gray, a sub-pixel micro-dot technique is used,varying the number of dots per unit area. As in the previously describedlaser/photographic camera, to produce multiple images in various placeson the film, the entire film image is first assembled and formatted inan electronic memory and then the film is exposed all at once, not imageby image.

FIGS. 4 and 5 are simplified illustrations of mechanical configurationsof the camera illustrated in FIG. 2. Thus, a camera housing 100 mountsthe cathode ray tube 50 adjacent an electronics housing 102 containinganalog to digital converter, multiplexer, monitor electronics and powersupply. The image of the face of the cathode ray tube is transmitted toa mirror 104 fixedly mounted in the housing which reflects the lightfrom the cathode ray tube face through the lens set 54 and the shutterset 56. Each shutter is positioned directly behind a respective one ofthe lenses. Camera housing 100 contains a film cassette 108 whichdetachably mounts the standard 8×10 inch film sheet 58. A light tightinner housing or enclosure 110 seals the area between the lens andshutter sets and the film cassette against entry of ambient light. Thelenses may have a 135 millimeter focal length with an aperture of F/16.With the monitor adjusted so that the CRT luminesce is 1.3 foot lambertsat the video white level and 20 foot lamberts at the video black level,exposure time to properly expose conventional medical video recordingfilm will be approximately one second for each color separation record.This exposure time may be obtained by employing a scan rate of one frameper second.

In FIGS. 4 and 5 the dotted lines 112a,112b,112c,112d,112e and 112frespectively represent the center lines of optical paths of the sixseparate images.

Viewer

FIGS. 6 and 7 illustrate respectively side and front vertical views ofan exemplary embodiment of a viewer for use with multi-monochromaticimage component records produced by the camera described above. In thisconfiguration the image record, namely the standard sheet film that hasbeen produced in the camera, is placed in the focal plane of a sixchannel optical projection system where it is illuminated from below bya multiple light source of the condenser type. Thus, in the illustratedexemplary embodiment, the viewer includes a generally upright viewerhousing 116 having a transverse frame 118 extending across anintermediate portion of the housing for supporting six condenser lensesof which those identified by numerals 120,122 and 124 are shown in FIG.6.

Also mounted on the intermediate transverse frame 119 and guided by sideguides 121 is a slidably extendable film drawer 128 in which is mountedthe film 58.

A second transverse support 130 is fixedly mounted to and within theviewer housing above the film holder and carries a trio of fixedprojection lenses 132,134,136 and a second trio of projection lenses132a,134a, 136a. These projection lenses (and the dual trios ofcondenser lenses) are arranged in the same off axis configuration as arethe lenses in the camera, so that the film images are projected to arear projection screen 140, mounted in the wall of housing 116, via areflecting mirror 142 that is also mounted in the viewer housing. Thearrangement is such that the projected images of each of the three imagecomponents of one set are precisely superimposed and of the same size asthe original cathode ray tube display.

At the bottom of the housing 116 are mounted six separate light sources144,144a,146,146a,148,148a, of which one is provided for each projectionlens and its associated condenser lens. Each light source employs a lampof the MR-16 type, having an integral ellipsoidal reflector of about twoinches in diameter. A lamp of this type has its filament positioned atone focal point of the ellipsoid so that an image of the filament isprojected out in front of the lamp, with this filament image being theobject of the condenser lens 120 through 124a in each of the sixprojection channels. Each condenser lens relays that filament imagethrough the film and into the aperture of the projection lens of its ownindividual channel, thus directing light from the source through thetransparent film image component to an individual one of the projectionlenses.

Red, green and blue color filters are provided in respective ones of theseveral viewer channels or light paths. In one embodiment these filtersmay be incorporated into and made a part of the individual projectionlens. A series of baffle plates, such as plates 150a,150b, etc., aremounted on fixed baffle plate supports 160 and 162 and provided with sixsets of aligned apertures of decreasing size. The apertures of each settaper from a relatively large aperture 164 for a lowermost plate 150n toa smallest aperture 166 at an uppermost one of the plates 150a. The sixrectangular apertures of graduating size in each of the baffle plateseffectively form six light directing tubes or tunnels for the six imagepaths from the six light sources to the six projection lenses. Only oneset of three lamps (for illuminating the three components of one image)is turned on to view one image. Accordingly, each of the threeindividual projection lenses of one set will receive light from oneentire image component but will not receive light from any of the othertwo image components of the illuminated set. Thus, stray light isprevented from contaminating individual images and degrading imagequality and contrast.

Each of the six lamps may be run at 100 watts so that during projectionof all three component images of one record the viewer will use 300watts. Each condenser lens has a focal length of 120 millimeters and isof aspheric shape to reduce its spherical aberration, which wouldotherwise cause uneven illumination of the image. The condenser lensesare cut into a rectangular shape instead of a round shape so each onecan be centered behind its film image and fully cover the entire imagewithout physical interference with an adjacent condenser lens. Thecondenser lenses are mounted very close to the film so that the filmimages are fully illuminated all the way to their corners.

The projection lenses have a focal length of 150 millimeters and anaperture of F/6.5. Color filters for each of the six channels aremounted on each of the individual lenses so that light projected in eachchannel has a different spectral content. The filters may be of theglass sandwich type, having a spectral characteristic equivalent toKodak Wratten types 29 red, 61 green and 47 blue. Of course other typesand locations of the color filters, with other spectral characteristics,may be employed to provide the required light of different spectralcontent for each of the six separate optical paths.

In operation of the viewer, with a film in the drawer and the drawer inposition, one of the two color images recorded on the film (in theformat illustrated in FIG. 1) is chosen for viewing by turning on thethree light sources which represent the components of the chosen image.The other three light sources are turned off. To view the second colorimage on the sheet film, of course, the first three light sources areturned off and the second three turned on. On the projection screen 140the three individual primary color image components of the singlecomposite record are superposed in precise registration and preciselyequal size to present a full color composite image.

In order to ensure precision registration on the viewer screen of allprojected images of one set of image components so that nomisregistration is visibly discernable to a person viewing the displayscreen 140, each group of three projection lenses employs a fixed centerlens, such as green lens 134, and a pair of adjacent adjustable lenses,such as red and blue lenses 136 and 132. Each of the adjustable lensesis mounted for adjustment in two mutually orthogonal directions in aplane perpendicular to the lens axis. Thus, as illustrated in FIG. 10,lens mounting plate 130 carries a horizontally adjustable horizontalsupport 150 upon which is slidably mounted a "vertically" adjustablevertical support 152, which itself carries a fixed lens mount 154 thatfixedly carries lens 136. Because of the angled mirror in the opticalpath of this vertically oriented viewer, X,Y adjustment of the lenses(in a horizontal plane perpendicular to the lens axes) results inhorizontal and vertical movements respectively of the blue and redprimary color images on the vertically oriented viewer screen.

Adjustable support 150 for lens 136 is adjustably operated by a rotarycontrol shaft 160 (see FIG. 10) which drives a screw 162 threaded to anut (not shown) carried by the horizontal support 150. A right angledrive 164 interconnects the screw 162 and rotary control shaft 160. Thelatter is rotated by a horizontal control knob 166 mounted on theoutside of the viewer housing 116. A vertical control knob 168 alsomounted on the outside of housing 116 operates a rotary control screw170 which is threadedly engaged with a nut (not shown) connected tovertical lens mount 152.

Similarly lens 132 has horizontal and vertical adjustable supports thatare respectively operated by a red control knob 174 via a rotary controlshaft 176, a right angle drive 178 and a threaded shaft 180 forhorizontal control of lens 132. A vertical red control knob 184 operatesa screw 186 threadedly connected to adjustably position the verticallens support of blue lens 132.

In a like manner, for the second image, which is projected by the secondtriad of lenses 132a,134a and 136a, there are provided vertical andhorizontal red control knobs 190,192 and vertical and horizontal bluecontrol knobs 194,196 that are actuated by mechanisms, identical tothose previously described, for X,Y (horizontal and vertical) adjustmentof lenses 132a and 136a of the first image projection system. Preferablythe adjusting screws have a very fine pitch to provide for small amountsof precision adjustment. By means of these adjustments the three imagecolor components on the projection screen can be brought into exactmutual registration by moving the red image component to preciselyoverlay the green image component and also moving the blue imagecomponent to precisely overlay the green image component.

The red and blue lenses of each triad of lenses may also be mounted totheir respective movable supports so that they can be moved in the Zdirection or axially of the lenses, but only as an internal or factoryadjustment. When the viewer is assembled during manufacture,magnifications in the three channels thus can be matched by moving thelenses axially one at a time so that the size of the red image ismatched to the size of the green image, and the size of the blue imageis likewise matched to the size of the green image. Precise matching ofprojected image component sizes is also critical for avoiding visiblydiscernable misregistration.

Illustrated in FIGS. 8 and 9 are details of the drawer 128 that isslidably and removably carried by the viewer housing and which isarranged to mount a sheet of film bearing color image components. Thedrawer comprises a rigid rectangular frame 200, having a drawer front202 and a handle 204 which is grasped to slide the drawer in and out ofthe viewer on support 118 and lateral drawer guides 121. Fixedly mountedto and within the exterior frame 200 is a skeletal film holder 206having front and rear members 208,210 interconnected with side members212 and 214. A longitudinal support member 216 extends between the frontand rear members 208 along the center line of the frame 206. Transversemembers 218,220 extend between side members 212 and 214, with all of themembers rigidly interconnected to one another and symmetrically disposedas illustrated to provide six separate viewing apertures 222a through222f. Each of the film image areas 222a through 222f has a size slightlygreater than the size of any one of the equal size image components ofthe film sheet, including a border of the image component, if any. Thefilm holder 206 is perfectly planar and provides a rigid flat supportfor the film sheet. Suitable means are provided to hold the film sheetprecisely flat and directly against the support so that all of the colorimage components of the film sheet will be at precisely the samedistance from the respective projection lenses.

For the purpose of holding the film against the film holder by ambientair pressure, a vacuum fitting 224 is provided on the inner end 200 ofthe slidable film drawer for connection to a source of vacuum (notshown). Vacuum fitting 224 is connected with a manifold or set ofconduits that extend to and through the film holder members 208, 210,212, 214, 218 and 220. Upper portions of all of these members areprovided with vacuum apertures, such as apertures 226, so that when asheet of film is placed on the holder 206 and a vacuum is drawn throughfitting 224 and all of the vacuum apertures, all six image areas of thefilm are held perfectly flat, in the same plane, against the film holderand thus are held equidistant from the projection lenses. The frame ofthe drawer may be provided with a finger aperture 228 to facilitaterelease of the film from the holder.

The film record is placed onto the film holder 206 of the drawer, whichis then closed. The drawer is slidably moved into the viewer on theprecision slides 121 which position the drawer accurately when closed sothat the film is precisely and repeatably positioned in the focal planeof the optical system. The bottom of the drawer where the film rests isvery thin, in the order of 0.080 inches so that the film can bepositioned close to the condenser lenses. The six rectangular imagecomponent areas of the film holder permit the light to shine through theimage components of the film. Each area is made slightly larger than theimage size on the film to allow for slight mispositioning of the film.Fitting 224 of the drawer connects with a flexible hose (not shown)which is connected to a vacuum source. A switch 223 (FIG. 6) is mountedto the viewer frame for actuation by the back of the film drawer whenthe latter is closed. The switch, when operated by the closed drawer,actuates a valve that initiates application of vacuum to the fitting 224so as to draw the film down to ensure that it is flat and that allimages are in focus. With all images in the same focal plane, allprojected and superposed images have the same magnifications (and sizeon the screen) and a precision registration of all projected superposedimage components on the viewer screen is better assured. When the draweris withdrawn, the vacuum controlling valve is operated to vent thevacuum system to atmosphere to facilitate removal of the film.

Other arrangements for holding the film flat and with all parts atprecisely the same distance from the lenses may be employed. Forexample, instead of the skeletal frame 206, the drawer may be providedwith a flat glass bottom and a second glass plate hinged to the flatglass bottom so that the film may be effectively sandwiched between apair of glass plates. However, the described vacuum system is preferredsince it does not require manipulation nor the care and cleaning of theglass that may be required to ensure clarity of transmission of lightthrough the glass.

If deemed necessary or desirable, the same switch that actuates thevacuum valve may also be connected to operate the power supply for thelamps in the light source of the viewer, whereby the lamps are energizedonly when the drawer is closed and the film is in position for viewing.

Various alternative arrangements of a viewer for projecting threemutually superposed images may be employed. For economy of optics, theviewer may employ three projection lenses instead of six (for a filmwith two pairs of triads of color image components). The three lenses,arranged in a vertical set, may be mounted as a unit to be mechanicallymoved from side to side so as to project either the three color imagecomponents of the first color image or of the second color image. Alllamps may be on at all times or the lens unit motion can be constructedand arranged to actuate switches that turn on an appropriate group ofthree lamps for illuminating the image selected for viewing.

As still another alternate arrangement, three projection lenses andthree light sources can remain stationary and the film in its drawer canbe moved from side to side to project either one or the other of thethree component color images.

With appropriate alteration of directions of the image paths, the viewercan be constructed and arranged to project both color imagessimultaneously in a side by side arrangement on a wider projectionscreen with six lamps on all at one time.

In the described viewer arrangement the color filters are mounteddirectly on the projection lenses. However, the filters may be placedanywhere in the light paths, either inside the lens assemblies, or at ornear nodal points which can decrease size and expense. The filters canalso be part of the light source, positioned at or near theconcentration of light flux so that the filters can be of decreasedsize.

As another option, instead of using six individual wide spectrum lightsources and selective filters to eliminate certain portions of the colorspectrum so as to yield the desired primary colors, the light sourcesmay themselves be colored, as, for example, by use of multiple differentcolor light emitting diodes or lasers.

Registration of Projected Image Components

In the description of the camera and viewer above, reference has beenmade to precision of positioning of the record images and to theprecision of the mutual registration and superposition of projectedimages in the viewer. Precise positioning of all three superposed colorimage components on the viewing screen is necessary to avoid discernablemisregistration. Human observers can easily see color fringes at theedges of superposed images. Normal human eyes, at a viewing distance ofabout ten inches, which is the closest that most normal eyes cancomfortably focus, will discern misregistration between two primarycolor images on a viewing screen where the misregistration is more thanabout 0.006 inches. Such discernable misregistration or color fringingmay not appear to be objectionable if the misregistration is 0.02 inchesor less. The color fringing is significant since it will adverselyaffect recognition of alphanumeric characters which are part of medicalultrasound pictures and which display date, examination site, patientidentification, etc. Further, in the clinical image areas of thepicture, color fringing may also adversely affect interpretation ofimages. Thus, it is of critical importance that the images on the screenof the viewer be so closely registered with one another as to avoiddiscernable misregistration. A goal of a maximum misregistration ofsuperposed images on the viewer screen of not more than 0.02 inches canbe achieved in several ways.

In one way of achieving such final precision registration of the threeimages components, the image components on the film record must beprecisely positioned with a predetermined relative positioning so thatwhen the film sheet is placed in a viewer having a fixed predeterminedrelative positioning of its lenses, the images on the viewer screen areprecisely registered with no discernable misregistration. This isaccomplished by critical positioning of any two of the image componentsrelative to the third. Alternatively, if the record image components arenot positioned on the sheet film relative to one another with sufficientprecision, the critical precision superposition and mutual registrationof projected image components may be achieved by adjusting the lenses ofthe viewer. Thus, the viewer lens adjustments described above may beemployed to compensate for erroneous relative positioning of the imagecomponents on the film record itself. To obtain sufficiently preciserelative registration and precise superposition of all three color imagecomponents on the viewer screen it is only necessary to move each of anytwo of the projections of the image components into precisionregistration with the third. Further, as will be described below, anautomatic registration (convergence) control may be employed in theviewer so that all three projected image components of a single colorimage will be automatically superposed in precision registration byautomatic adjustment of two of the lenses of a triad. This automaticconvergence control employs a film record having reference indiciaformed in precision predetermined locations adjacent each imagecomponent.

For proper mutual registration of the viewed images, the overall systemmust account for both image component position and size. In a presentlypreferred embodiment of the viewer, magnification is 1.26x from the filmto the screen. This means that position and size accuracy referred tothe film must be within 0.0048 inches for the above mentioned 0.006 inchmisregistration limit or must be 0.012 inches for the 0.020 inchmisregistration. These maximum misregistrations are the maximum totalrelative positioning and size errors between any two of the three imagecomponents on the film record.

Both the camera and the viewer can be adjusted during manufacture sothat the sizes of the three images match almost perfectly. Sizeadjustment is accomplished by adjustment of the axial positions of thelenses to alter the magnification. Absolute image size is of relativelylesser concern since it is only necessary to match the size of two ofthe image components to the third. Any defocusing caused by such slightaxial adjustment in order to match magnifications will not result in anydiscernable image degradation. Accordingly, for all practical purposes,system errors due to image size variations between the three channelsmay be considered to be negligible.

Errors due to lateral image displacement, that is, errors in relativepositioning, are of greater significance. Again it is not necessary toobtain absolute image positions, but only to obtain relative positionsof two of the image components relative to the third.

Thus, if no adjustments are to be made in the viewer with respect torelative position of the projected images, it is necessary that thecamera system for making the film record be constructed and arranged sothat the image components exposed on the film sheet have a maximumdeviation between any two of the triad of images of not more than about0.0048 inches. Assuming that the viewer contributes no furtherregistration errors, and further assuming that no adjustments are madein the viewer, this precision of image positioning of the imagecomponents on the film record is more than adequate to preserve themutual registration required to prevent any discernable appearance ofcolor fringing or other misregistration on the viewer screen, even to avery critical observer. However, even with such precision registrationof relative position on the film record, it may still be desirable toensure that the contribution of the viewer to any misregistration errorsis substantially zero. Therefore, the viewer incorporates operatorcontrolled convergence adjustments that enable X,Y motion of two of theimage components relative to the third by translational motion of thelenses. Such adjustment allows any misregistration or misconvergenceerrors of the displayed superposed images to be nulled out. Once such anadjustment of the viewer is obtained, registration will be perfect or atleast acceptable for all films produced by the camera which produced thefilm that is used for the user convergence adjustment of the viewer. Theregistration will be critically acceptable for films produced by anyother camera which are within 0.0048 inches of misregistration.Furthermore, the convergence adjustments on the viewer serve the addedpurpose of providing an ability to properly display (without discernablemisregistration) film produced by other cameras that may be abnormallyout of register, including cameras built by manufacturers other than theone that builds the viewer itself.

Another problem that may affect registration accuracy is the shape ofthe image, that is, its deviation from perfect rectangularity. If theshape of the three image components of the color image are not the samethey cannot be brought into register in all parts of the compositeimage. In the described system two factors affect image shape. One isany difference in the shape of the objects being photographed, that isthe shape of successive displays on the CRT. Another is the effect ofdifferential optical distortion of the images because optical systems inboth the camera and the viewer are off axis.

With respect to the first factor, shape of the displayed image on themonitor need not be perfectly rectangular as long as it does not changebetween the recording of the three successive color image components. Ifit does not change during the recording of the three components, all thethree distortions will match one another.

The second factor, differential optical distortion, is due to the factthat the three optical systems are off axis in different directions forthe three images of each trio of images, as illustrated in FIG. 3. Eventhough the lenses themselves are rotationally symmetrical about theirindividual axes, these axes intersect the images at different pointswithin each image so that any off axis optical distortion affectsdifferent parts of the three different images. However, the viewer andcamera described herein are provided with optical systems in the viewerand camera that are reciprocally similar. Therefore, the effects ofthese distortions in the camera and the viewer cancel. Accordingly, evenif the shapes of the individual images on the film do not quite match,they will match when projected on the viewer screen. In order toaccomplish this matching, the magnification in the camera is thereciprocal of the viewer magnification. The recording lenses in thecamera and the projecting lenses in the viewer are of similar opticaldesign and face in opposite directions. They are of approximately thesame focal length, and the optical dimensions of the camera and viewerare approximately reciprocally symmetrical. Thus to avoid this opticaldistortion in an exemplary system, viewer magnification is 1.26X andcamera magnification is 0.79X, the reciprocal of 1.26X.

The reciprocal symmetry between camera and viewer optics has anothersurprising and unexpected beneficial effect. This effect is correctionof color shading due to differential illumination fall-off in the cameraand viewer optical systems. All lenses except some very special onesexhibit a fall-off in image illumination as the field angle increases.In the camera described above employing a lens of 135 millimeter focallength, with off-axis lens and image positions as shown in FIG. 3, theillumination at the farthest corner of the image is approximately 73% ofillumination on the lens axis. This causes a gradual change in filmdensity in each image as one moves away from the lens axis. Since thethree lens axes intercept the three film images in different places, asshown in FIG. 3, density change will be rotationally symmetrical arounddifferent points on the various color image component records. Thedensities of the three images control the amount of colored lightprojected on the viewer screen in each of the three color channels. Thusit may be expected that the primary colors would add togetherdifferently in different parts of the composite color image projected onthe viewer screen, causing undesirable changes in hue in different partsof the field.

However, as previously mentioned, the silver-halide video recording filmproduces a positive image because the inversion of the Z-axis signal fedto the CRT causes the CRT to display a negative image. The positive filmimage is dark where it is exposed to light from the CRT and transparentwhere it receives no light. This inversion is achieved, as previouslymentioned, by electrically inverting the video signal in the camera sothat the "black" video level produces high brightness on the CRT to makethe film image dark and the "white" video level produces low brightnesson the CRT so that the film image will be transparent. The result isthat the density of the film in each image is darkest on the lens axisand becomes lighter away from the lens axis (which is not the same asthe image axis). In the viewer the same off-axis light fall-offphenomenon in the projection optics produces more light on the lens axisand brightness falls away toward less light as distance from the lensaxis increases. Because the optical systems in the camera and viewer arereciprocally symmetrical (e.g. the magnification of one is thereciprocal of the other), and particularly because the relationshipsbetween the lens axes and image axes are the same in the camera and theviewer, the asymmetrical illumination fall off effect of the camera andthe corresponding effect of the viewer on the viewer screen image willbe in opposite directions. The higher light flux on the projection lensaxis is more attenuated by the darker density of the film on the lensaxis. In actuality, the cancellation is not exact because of the effectof the film characteristic, but the effect is nevertheless sufficientlysignificant to make the color shading undiscernible.

In the system arrangements described above, required accuracy ofsuperposition of the separate projected primary color image componentson a viewer screen is accomplished primarily in the recording process byprecise location of the color separation image components on the film inthe camera and by precise positioning of the images in the viewer. Inthese systems, adjustment of the viewer for minimizing misregistrationis not necessary or need be performed but one time. This requires,primarily, a precision camera and use of the same camera or a camerawith equivalent precision positioning to make records having preciselypositioned image components for the viewer. However, for the film recordproduced by a camera having less than the desired precision of relativepositioning of the color image component, the viewer lenses must beadjusted to properly register color image components on the screen. Forexample, described below and illustrated in FIG. 17 is an adapter thatenables a conventional camera to form the sets of color image componentsof the system described above. Because such conventional camera may notproduce film image components positioned with requisite precision, theviewer may be required to compensate for the lack of precisionpositioning. To this end the viewer may be provided with automaticconvergence, as will be explained in the following description.

Automatic Convergence

An alternative approach to precise image positioning on the record asachieved by a precision camera, is to modify the viewer so as toautomatically adjust its optical system so that the viewer automaticallyachieves good superposition of image components even though the imagecomponents may not be accurately positioned on the film. This approachis somewhat more complex but avoids the problem of requiring a filmrecord made by a camera of very high precision and stability, and allowseven previously designed black-and-white cameras to be adapted for useas components of the described system. Such adaptation of a conventionalcamera will be described hereinafter.

A viewer with automatic convergence will project components from arecord in which the image components are not relatively positioned withsufficient precision, and will project them on the screen of the viewerwith relative positioning having a maximum error that avoids discerniblemisregistration. In general, this automatic convergence control isaccomplished by causing the camera to place a fiducial or reference markon the film at a predetermined position with respect to each of thecolor image components. The viewer employs these fiducial marks asreferences and automatically adjusts viewer lenses to bring theprojected images into precise superposition. If each of the fiducialmarks on the film record have the same spatial relationship to each ofthe separate images with which the respective fiducial marks areassociated, then when the projections of fiducial marks are brought intoregistration in the viewer, the associated images will also be inregistration with each other, that is, they will be preciselysuperimposed. Portions of a viewer for accomplishing such automaticconvergence control is illustrated in FIGS. 12 through 16.

FIG. 12 illustrates a sheet film 300 substantially identical to thesheet film 16 of FIG. 1, having image components 18 through 28 just asdescribed above in connection with FIG. 1. However, the camera ismodified to provide, in addition to the color image components, fiducialspots such as spots 302, 304, 306, 308, 310 and 312, each having apredetermined position with respect to its associated image. Thus, spot302 has a predetermined position with respect to its associated image18. Spot 306 has a same predetermined position relative to itsassociated image 20, etc. The spots are made on the film close to eachof the associated color image components by producing a light or darkspot on the face of the CRT at the same time that the pictorial rasterof a particular image component is produced. The fiducial spot and theimage component on the face of a CRT are exposed or photographed ontothe film at the same time. The spot is positioned outside the rasterimage area but is within the field of view of the camera optics.Conveniently, the spot may be produced by the monitor, during verticalretrace interval, by briefly deflecting the cathode ray tube electronbeam to the desired position of the spot and simultaneously unblankingthe beam for a short time. This is performed by a simple and knownmodification of the CRT control electronics, which is schematicallyillustrated as a spot control circuitry 316 forming part of a controller78 of FIG. 2.

A viewer modified for automatic convergence control includes a sensorand a set of filters for sequentially sensing position of the referencespots for a set of red, green, and blue image components andautomatically moving the red and blue lenses so as to ensure precisionsuperposition of all of the three sensed spots. This ensures precisionregistration of the three projected color component images. The opticsof the viewer project the three fiducial spots together with the threeimage components of each set onto the common focal plane, which is theplane of the viewing screen. If the three separate color images on thescreen are not in register, the three projected reference spots, whichare projected in the same colors as each of the associated imagecomponents, will not be in register either. By automatically bringingthe spots into mutual registration the pictorial image components arealso brought into register.

Arrangement of the viewer for the automatic convergence control may beidentical to that shown in FIGS. 6-11 except that automatic adjustmentinstead of manual adjustment of red and green lenses in X and Y isprovided for both image sets.

In general, a sensor detects misregistration of the projected colorreference spots and develops an error signal if the spots are not inregister. This error signal is used to drive actuator motors that movethe lenses in a sense to decrease the error signal so that the fiducialor reference spots are moved more closely into registration. Thus, aclosed loop control is provided for the automatic convergence ofprojected images.

An arrangement of closed loop automatic convergence control isillustrated in FIGS. 13, 14 and 15. FIGS. 13 and 14 show the mounting ofthe sensor adjacent the viewer screen, it being understood that allother parts of the viewer previously described remain the same exceptfor the fact that the manual control of adjustable lens position isreplaced by motor control, as will be explained in connection with FIG.15.

Mounted adjacent screen 140 of the viewer is a two dimensional CCDoptical sensor array 230. The sensor is positioned with respect to thescreen in a position in which the reference spots of the record filmwill be projected. As the reference spots have a fixed predetermined andknown relation on the record film with respect to the image components,the sensor may be fixedly positioned in an appropriate location withrespect to the screen. A filter wheel 234 rotatably carried in a hub 236that is fixedly mounted in the viewer, is selectively driven by astepper motor 238 and carries red, green and blue color filters 240,242, and 244, respectively. The color filters are positioned adjacentthe periphery of the wheel, so that, as the wheel is rotated the filterswill sequentially pass in a position between the sensor and theprojecting lenses of the viewer, momentarily stopping in such position.The filter wheel and filters 240, 242, 244 do not affect projectingimage components. The projected red, green, and blue light passes to therespective color filters in sequence, with light of only one colorpassing through the respective filters 240, 242, 244 to the sensor atany one time. The size of the sensor array is sufficient to encompassthe entire area over which the reference spots might be projected. It isnot necessary that the reference spots have any fixed absolute positionas long as they are all positioned in the same relation with respect tothe associated color image component and within areas that ensureprojection of the spot on a part of the sensor. The array may have asize of about 0.500 by 0.500 inches to provide a pixel array of 1024×1024 which will yield position resolution of 0.0005 inches. Suchresolution is more than adequate to achieve the 0.006 inch imageregistration accuracy that is required as previously described.

The color filters are employed to distinguish between the referencespots associated with the individual color images. For example, if thered filter 240 is positioned over the sensor, the sensor will see onlythe reference spot associated with the red color image component sincethe latter is projected by the viewer with red light when all film imagecomponents are simultaneously projected. Further, the red filter willblock blue and green light which project the blue and green color imagecomponents simultaneously with the projection of the red component.During this simultaneous projection of the three image components, thefilter wheel is driven by the stepper motor to cause the three colorfilters to be sequentially positioned, and momentarily stopped, in frontof the sensor. Positioning of the sensor wheel is controlled in part bya home position sensor 250 fixedly mounted to the viewer to sense andsignal a reference position of the sensor wheel. The home positionsensor is a conventional infrared optical interrupter which senses anotch in the edge of the wheel. The motor is positioned at the homeposition sensor when the green filter, for example, is in position overthe sensor array 240.

As shown in FIG. 15, sensor 230 receives light through one of the red,green or blue filters projected by the red, green and blue lenses whichare indicated in FIG. 15 by reference numeral 251, 252, and 254. Aspreviously described, each of the red and blue lenses is mounted on lensstages or supports 256,258 respectively, which are moveable in both Xand Y directions. Lens support 256 is driven by a red X stepper motor260 and a red Y stepper motor 262. Similarly, the blue lens support 258is driven by a blue X stepper motor 264 and a blue Y stepper motor 266in the two mutually orthogonal directions. The sensor output signal isfed to a signal conditioner 270 and then through an analog-to-digitalconverter 272 to a lens controller 274 which calculates coordinates ofthe red and blue spots and compares these with the coordinates of thegreen spot to selectively drive the four stepper motors 260 through 266via stepper controllers 280, 282, 284 and 286. Controller 274 alsocontrols operation of the filter wheel by sending a signal via a filterstepper motor controller 288 to the filter stepper motor 238. Homeposition sensor 250 sends a signal to the controller for use and controlof filter wheel position and also sends a signal via clock logic 290 tocontrol scanning output of the sensor array.

In operation of the described automatic convergence control, the filterwheel is first sent to its home position, placing the green filter overthe sensor and allowing the latter to be illuminated by only the greenspot which falls somewhere on the sensor. After a short period in thisposition, the filter wheel is rotated by its stepper motor to place thered and blue filters successively over the sensor. The filter wheelstops momentarily when each filter is at the sensor, allowing it to seeonly red and blue spots, one at a time. These steps are performed whileall three image components are projected on the screen. To sense theposition of each color spot, the sensor data is clocked from the sensorin a conventional manner and sent through the signal conditioner, whichnormalizes the data, and then through the analog to digital convertorinto the controller which has an appropriately programmedmicroprocessor. In the controller microprocessor a stored algorithm ofconventional form calculates coordinates of the centroid of each spot.This positional information is used to adjust the viewer optics, movingred and blue lenses in X and Y so as to achieve automatic preciseregistration of the three color image components on the screen.

Using coordinates of the green spot as a reference, the microprocessorcalculates positional errors of red and blue spots as coordinatedifferences. The differences are scaled by the ratio of stepper countsper pixel of the sensor, and signals are sent to the stepper controllers280 through 286 for X and Y positioning of the red and blue lenses. Thecontrollers respectively drive the four individual lens adjustmentstepper motors 260 through 266 to move the adjustable supports on whichthe lenses are mounted. The lenses are thus moved to new locations wherethe positional coordinates of all three colored spots on the sensor arethe same. When the spots are in register the color image components arealso in register.

The cycle of correction is initiated when film is placed in the viewerfilm drawer and the drawer is closed, bringing film into position forprojection. Switch 223, operated when the film drawer is closed (SeeFIG. 6), is connected to initiate the automatic convergence controlcycle in addition to initiating application of the film holding vacuumsystem and turning on the lamps. A short delay such as about 5 secondsis provided after closing the drawer to allow the film to beappropriately flattened by the vacuum hold down.

FIG. 16 illustrates operation of the microprocessor program ofcontroller 274. As shown in this flow chart, the system waits for thedoor to be closed, block 300. Upon closing of the door a 5 second delayis initiated, block 302. Then the filter wheel is rotated to its homeposition, block 304, in which the green filter is positioned at thesensor. With the sensor information provided to the microprocessor thecentroid of the green spot on the sensor is then calculated and itsvalue stored, block 306. Now the filter wheel is again rotated toposition the red filter into the light path adjacent the sensor, wherethe wheel momentarily stops, block 308. Then, as indicated in block 310,the microprocessor calculates the centroid of the red spot and, block312, subtracts the coordinates of the red spot centroid from the storedcoordinates of the green spot centroid, scaling these differences toprovide the appropriate number of counts to drive the red steppermotors. The calculated stepper motor counts are then fed to the steppermotors to move the red stepper motors as indicated in block 314.

Having positioned the red lens into precision registration of theprojected red and green images, the filter wheel is rotated to positionthe blue filter in the light path, where the wheel momentarily stops, asindicated in block 316. With the blue filter positioned in the lightpath the sensor sees only the blue light projected through the bluereference spot and can then calculate coordinates of the blue centroidas indicated in block 318. The calculated coordinates of the bluecentroid are subtracted from the stored coordinates of the greencentroid and an appropriate number of stepper counts is scaled for eachof the X and Y blue stepper motors as indicated in block 320.

The blue stepper counts are fed to the blue stepper controllers to movethe X and Y blue stepper motors, block 322, thereby positioning the blueimage component in precision registration with the green imagecomponent. Operation of the stepper motors to adjust lens position movesthe projected image components into more precise registration. Thus, allthree projected image components are now precisely superimposed with therequisite precision. The system will then wait for the drawer to open asindicated in block 324, and return control to the start of the automaticconvergence control cycle, block 300.

Conventional Cameras

Cameras specifically designed to provide the described three imagecomponent film records and having image component positioning ofrequisite precision are used to make film records for projection by theviewer of FIGS. 6-11. However, concepts of the present invention may beused in conventional, existing black-and-white multi-image cameras, withvarious types of modification, or with an external adapter, as will bedescribed below. To afford a better understanding of adaptation of thepresent invention to known or existing equipment, some commonconventional camera systems and operations will now be described.

Diagnostic ultrasound black-and-white images are usually recorded onfilm which is 8×10 inches, with 6 separate images on each film. Theformat of the images on the film is as illustrated in FIG. 1. It isuseful to designate the arrays of image component and lens locations asshown, for example, in FIGS. 1 and 3, as an array of two verticalcolumns, each having three horizontal rows. In a conventional camera,image positions, but not sequence of exposure, are as shown in FIGS. 1and 3. Thus, the three components 18,20,22 of the first color image asshown in FIG. 1 are positioned on film 16 with the red component of thefirst color image in the upper left corner (Col. 1, Row 1). The greencomponent 20 of the first image is positioned in the center of the leftside (Col. 1, Row 2), and the blue component of the first color image inthe lower left corner (Col. 1, Row 3). The components of the secondcolor image of the two images formed on the standard 8×10 inch film arealso positioned as illustrated in FIG. 1, with the red component of thesecond image in the upper right corner (Col. 1, Row 1). The greencomponent of the second image position is in the center of the rightside (Col. 2, Row 2), and the blue component of the second imageposition is in the lower right corner position (Col. 2, Row 3) of thefilm. The conventional black-and-white camera locates its six images inthe same positions, but in the following sequence: Position 1 (Col. 1,Row 1), Position 2 (Col. 2, Row 1), Position 3 (Col. 1, Row 2), Position4 (Col. 2, Row 2), Position 5 (Col. 1, Row 3), and Position 6 (Col. 2,Row 3).

During a diagnostic ultrasound examination procedure, when the medicalsonographer wishes to record an image that is observed on the viewingscreen of the ultrasound scanner console, a button or a footswitch ispressed to initiate a film recording cycle. For a new sheet of film, thefirst image is normally recorded at Position 1, in the upper left-handcorner. The next time an image is recorded, it is placed at Position 2,etc. When all 6 positions have been used for recording images, the filmis full and another sheet of film is used for further images, startingat Position 1 again. The operator need not be involved in placing theimages; the equipment takes care of doing that. The individual imagescan be identified by date and time information which is incorporated ineach image.

There are various kinds of apparatus for producing film records of thistype and format. Such apparatus are known variously as cameras, filmrecorders, or printers, and they use various technologies. Some of theseare described above. Sometimes there is a direct connection between asingle diagnostic ultrasound machine and a single camera which isdedicated to it; sometimes one camera or printer is shared by severaldiagnostic ultrasound machines. In the latter case, sometimes the piecesof equipment are wired together and electronic multiplexing is used todirect the electronic images in the network; or sometimes the electronicimages are captured or commanded by an acquisition unit at eachdiagnostic ultrasound machine, using disks or tape, which are laterphysically taken to a shared camera for recording on film.

A common configuration, particularly in small installations, is use of asingle camera dedicated to a single diagnostic ultrasound machine.Usually, the camera is mounted in the ultrasound cart, so that it ispermanently wired to the ultrasound machine, being disconnected only formaintenance or repair.

Currently the most common type of camera for dedicated applications isone that is CRT-based. The video signal from the ultrasound machine,usually a standard EIA RS-170 composite black-and-white video signalcontaining the same electronic image which is displayed on theultrasound console screen, comes into the camera on a cable. If thecamera is connected to a diagnostic ultrasound machine which has coloras well as black-and-white capability, then when the ultrasound machineis in black-and-white mode its camera output is as above; but when theultrasound machine is in its color mode its camera output is a similarsignal containing only the Y or luminance component of the electronicimage. In the camera, the video image (with or without intermediatesignal processing) goes to an internal video monitor, where it can bedisplayed on command by the internal CRT. An optical system projects theCRT image onto the film and a photographic snapshot is taken. Usuallythe film used in cameras like this is so-called video recording film,which is similar to silver-halide X-ray film except that it is coatedwith light-sensitive emulsion on only one side. The film can be quicklyprocessed in conventional X-ray film processors in radiologydepartments. It may be noted that, for illustrative purposes, both thedescription of the system embodying the present invention and itscomponents and the description of conventional black-and-whitemulti-image cameras in this section refer to CRT-based, dedicatedcameras that use video recording film. Nevertheless, film for thedisclosed system can be produced by any means which puts six preciselysized and precisely located images on a sheet of film. Use of themulti-component system disclosed herein is not limited to a CRT-basedcamera.

In CRT-based cameras of this kind, there are various ways ofdistributing the successive images to their proper places on the film.In some cameras there are six separate lenses, each of which projectsthe CRT image to a different position on the film. The lenses arenormally blocked by a shutter or shutters, and one at a time isunblocked to take a snapshot of the CRT. In some there are two lenseswhich are shuttered to take snapshots in positions 1 and 2. Then, eitherthe lenses are moved or the film is moved and snapshots are taken inpositions 3 and 4, and after another movement, in positions 5 and 6. Insome cameras there is a single lens which moves to multiple positions,and in some the CRT moves as well. The same effect can be accomplishedby moving mirrors in the image path to various positions. Yet anothertechnique is to assemble all of the images, one by one, into anelectronic memory, and then display them all at once, properlyformatted, on the CRT face and take a single snapshot of the entirearray on the film.

These cameras sense when a new film is inserted, and set the internalcamera controller to place the first image in position 1, the next imagein position 2, etc. Frequently there are front-panel indicators tosignal which image position is the next active one. When the 6 positionsare used up the camera will record no further images, and it signals theoperator to change the film.

As part of the image recording cycle there is usually an internallycontrolled calibration routine to keep film exposures consistent so thatdensity range is the same for all images. A common way to do this is todisplay a test pattern on the CRT, with shutters closed, before eachexposure, look at it with a calibrated photocell, and automaticallyadjust either the exposure time or monitor brightness and contrast.

The control panel of a typical camera usually contains several controlsand indicators. The controls may include a power switch, an inputselector, if more than one video input can be accommodated, a videoinvertor to choose between a positive and a negative image on the film,controls for setting exposure parameters, including monitor contrast andbrightness and exposure time, an "expose" button to initiate the imagerecording cycle, and an "advance" button to increment the next activeimage position ahead one step without recording an image. This lastfunction allows exposing of images in positions that are out of thenormal sequence. If an image position is skipped by using the "advance"feature, then after the highest-numbered image position is exposed, theexposure sequence "wraps around" to the lowest-numbered unused positionand then uses the remaining unused positions in ascending order untilthey are all used up.

Among the control panel indicators of such conventional camera isusually a group of lights which indicate the 6 image positions on thefilm. Typically, a light will be green if that position has not beenexposed yet, red if it has already been used, or flashing red/green ifit is the next active image position to be exposed. The control panelmay also have indicators to show positions of various controls, and analphanumeric display which can be selected to show the values ofexposure parameters which have been set.

External electrical connections of these existing cameras usuallyinclude one for power, one for video input (sometimes 2 which can beselected by a switch), and one for externally initiating the imagerecording cycle. The latter can be connected to a footswitch or to thekeyboard of the host ultrasound machine. Many cameras also have an EIARS-232 digital control port through which signals that duplicate all thefront-panel controls and indicators can be sent to and from the camera.Using that port, external equipment can be connected to the camera tocontrol its functions, set its conditions, and receive information aboutits status. The RS-232 digital control port can be used with an externaladapter, to be described below, to make a conventional black-and-whitecamera operate as a part of the system disclosed herein.

It may be noted that when a camera of the type described above and shownin FIGS. 2-5 herein is in its black-and-white mode, which is when thehost ultrasound machine to which it is connected is in its ownblack-and-white mode, the camera behaves like a conventionalblack-and-white camera described in this section, and produces filmswith six different black-and-white images in the conventional positionsand sequence.

Adapter for Existing Cameras

Systems of the present invention, which have been described above inconnection with FIGS. 1-16, have used cameras originally designed towork as part of the system. But in some situations, it may be desirableto consider adapting conventional black-and-white multi-image cameras towork in the novel system disclosed herein. Such adaptations can be at 3levels: (a) modifications to existing camera designs, permitting newcameras to be manufactured with the new capability without completeredesign; (b) modifications to existing cameras, either in the field orat the factory, to adapt them to work in the new system; (c) addition ofan external adapter to existing cameras to give them capability of thenew system with no internal modifications, or at most some changes inadjustments. There are a great many conventional multi-image camerasalready installed at sites where upgrading to novel systems disclosedherein might be desirable, so the advantage of adaptation of existingcameras is significant.

In order for existing cameras to be candidates for adaptation to thenovel system disclosed herein without degrading performance, they musthave some special characteristics: (a) size, placement, and matching ofimages on the film must be compatible (or adaptable to being madecompatible) with the attributes of the described viewers; (b) opticaldistortion and density shading of images must be low enough to assureadequate registration and color consistency of displayed compositeimages; (c) mechanical stability of the structure must be adequate toassure repeatability of optical performance; (d) the camera's electroniccontroller must have the latent capability of being converted to placethe separate color record images in the color component sequencedescribed above, such as by means of a digital control interface whichprovides a window into the camera controller. All existing conventionalcameras may not meet these requirements.

Two basic capabilities must be added:

A. The camera has to accept electronic images in color video form,preferably in RGB format, and it has to be able to switch among thecolor components.

B. The camera has to select the color components and direct them so thatthey are automatically recorded in their proper places, in propersequence, on the film.

These added capabilities are readily provided by the adapter describedbelow.

Typically, a diagnostic ultrasound machine with color capability willhave its video image output in the form of 4-line color, i.e. R, G, B.and sync. The separate color video signals are in conventional RS-170form, but they do not contain composite sync information; instead, thesync is on a separate line. When the ultrasound machine is inblack-and-white mode, the only difference is that the signal on all 3color channels is the same. Conventional black-and-white cameras do notaccept video signals in this form. Their video input capability is forsingle-line monochrome RS-170 composite video signals, containing syncinformation on the same line.

Illustrated in FIG. 17 is an adapter for use with a known multi-imageblack-and-white camera, that is normally arranged for accepting suchsingle-line monochrome RS-170 composite video signals. Such a camera isillustrated in FIG. 17 at 330 and may be, for example, the Aspect orFrantz 810 camera, having characteristics described above. An adaptorgenerally indicated at 332 is provided to receive signals from theconventional color ultrasound scanner such as the scanner 10 of FIG. 2,and put these signals in a form that enables the multi-imageblack-and-white camera 330 to produce multi-component color imagecomponent records. The existing multi-image camera 330 includes suitablearrangements such as a plurality of lenses, for example, that enablesthis camera to expose on a conventional standard 8×10 inch sheet film aplurality of images in the common six image format and position sequencedescribed above. The adapter provides the signals and controls therequired functions to feed the appropriate color component signals tocamera 330 and simultaneously to control its CRT blanking and shuttersfor placement and exposure of the three red, green, and blue color imagecomponents on the sheet film in the positions required for the viewerdescribed above. These positions, as previously described (FIG. 1) areimage component locations 18, 20, 22 for R, G and B components of afirst color image, and image component locations 24, 26, 27 for R, G andB components of a second color image. Thus the adapter, as one of itsfunctions, changes the image positioning sequence of the conventionalcamera.

The four-line video from the diagnostic scanner is provided on lines334, 336, and 338 as the red, green and blue components, respectively,and includes a sync signal on a line 340. The three color video signalsare fed to an adapter multiplexer 342, that is controlled by an adaptorcontroller 344 which basically performs the functions of the controller76 of FIG. 2. The multiplexer is controlled to select one color at atime, to be fed to a composite video generator 346 which also directlyreceives the sync signal on line 340. The composite video generatorproduces a video signal in the standard RS-170 composite monochromevideo format with sync included, and contains the video portion of theselected color image component. This video signal is fed to the videoinput of the conventional camera 330.

Adapter controller 344 is provided with two selectable microprocessorprograms, one for color mode and one for black-and-white mode. Selectionof color or black-and-white is made by an externally controlled modeswitch 350. A signal on an externally controlled command line 352connected to the controller 344 initiates an exposure cycle either incolor or black-and-white. Controller 344 is also connected to themultiplexer to select the appropriate color component. The controlleralso has a connection via a line 354 to the standard RS-232 controlinput of camera 330. Appropriate commands are formatted in accordancewith RS-232 protocol and stored in the controller memory to betransmitted under program control to the camera controller in order toinitiate camera functions or to be recognized by the adapter controllerin order to indicate camera status.

When in color mode, as selected by the adapter mode switch 350, and whena new film is in the camera, the following sequence of steps isperformed under control of the microprocessor program upon occurrence ofan expose command on line 352 to the adapter. Control signals from theadapter to the camera, and status signals from the camera to the adapterare transmitted by RS-232 interface connection 354.

A) The expose command line is locked so that another expose command willnot be accepted until the entire exposure sequence is completed.

B) The multiplexer selects the red video signal component from thescanner and generates a composite monochrome video signal from this redsignal component, sending that signal to the camera. An internal exposecommand is sent from the adapter to the camera control and initiates anexposure cycle in the camera.

C) The image, which is that of the red image component, is recorded atposition 1 (Col. 1, Row 1) of the camera. As mentioned above, in normaloperation of the standard camera images are recorded in sequence inpositions 1 through 6 in black-and-white. Thus, the first exposure (red,for example) controlled by the adapter in color mode is at position 1(Col. 1, Row 1). The camera's controller sets the next exposure to bemade at position 2 (Col. 2, Row 1), but this is not the desired locationof the next (green) component, so position 2 will be skipped.

D) After receiving a ready signal from the camera's controllerindicating that the first exposure has been completed the adapter sendsan "advance" command to the camera causing the camera controller to setthe next exposure to be made at position 3 (Col. 1, Row 2). Position 2is skipped at this time.

E) The adapter multiplexer next selects the green video signal from thescanner, generating a composite monochrome video signal and sending thatsignal to the camera.

F) An internal expose command is sent to the camera which initiates anexposure cycle as in step B. The image of the green component is thenrecorded at position 3 and the camera controller sets the next exposureto be made at position 4 (Col. 2, Row 2). Position 4 will be skipped atthis time.

G) After receiving a ready signal from the camera an "advance" commandis sent to the camera causing its controller to set the next exposure(blue component) to be made at position 5.

H) The multiplexer now selects the blue signal from the scanner,generates a composite monochrome video signal and sends it to thecamera.

I) An internal expose command is sent to the camera which initiatesanother exposure cycle. The blue image component is then recorded atposition 5 and the camera's controller sets the next exposure to be madeat position 6 (Col. 2, Row 3).

J) After receiving a ready signal from the camera an advance command issent to the camera. The controller then attempts to set the nextexposure to be take at position 1 ("wrap-around"), but finding thatposition has already been used, moves to position 2 as the next activeposition. Thus, the three color image components of the one color imagehave been recorded at positions 1, 3 and 5 which are the same aspositions of the image components 18, 20 and 22 of FIG. 1.

K) The external expose input command to the adapter is unlocked so thatanother exposure of three color image components can be initiated.

The next three-part exposure of a second color image on the same filmtakes place according to the following sequence, after a second exposecommand is given to the adapter.

L) External expose command line is locked.

M) The multiplexer selects the red video signal (at the second image)from the scanner and generates a composite monochrome video signal thatis sent to the camera.

N) An internal expose command is sent to the camera which initiates anexposure cycle. The red image component is then recorded at position 2(Col. 2, Row 1) on the film and the camera's controller tries to set thenext exposure to be taken at position 3 (Col. 1, Row 2). Finding thatposition is already used, the camera moves to position 4 (Col. 2, Row 2)as the next active position. (As previously mentioned, the standardcontrol circuitry of the conventional camera provides means fordetermining whether or not a position at which an exposure is to be madehas been previously used and, if so, advances the camera to cause anexposure at the next succeeding position.)

O) After receiving a ready signal from the camera, the multiplexerselects the green video signal and generates a composite monochromevideo signal that is sent to the camera.

P) An internal expose command is sent to the camera which position 4(Col. 2, Row 2) on the film. The camera's controller tries to set thenext exposure to be taken at position 5, but finds this position alreadyused and moves position 6 (Col. 2, Row 3) as the next active position.

Q) After receiving a ready signal from the camera the multiplexerselects the blue video signal, generates a composite monochrome videosignal and sends it to the camera.

R) An internal expose command is sent to the camera which initiates anexposure cycle. The blue image component is recorded at position 6 onthe film.

S) The film is now completely used. All six positions have recordedimage components thereon in the positions needed for the viewer and thecamera signals the operator to change film. After the new film has beeninserted, the camera sends a ready signal to the adapter causing it tounlock the external expose command line whereby the system is now readyto start over to record two additional images.

If the adapter has been set in the black-and-white mode by the modeselector, the sequence is different. When an expose command is given tothe adapter and a new film is in the camera the following steps areperformed under command of the adapter controller 344.

The multiplexer selects the line of the green video signal, generates acomposite monochrome video signal and sends that to the camera.

U) An internal expose command is sent from the adapter to the camera viathe interface command line 354 which initiates an exposure cycle in thecamera including any pre-exposure calibration routine that the cameramay employ. The image, which is that of the monochrome image from thescanner, is recorded at position 1 on the film. The controller of thecamera 330 then sets the next exposure to be made at position 2, whichis the standard sequence of the conventional camera.

The next time the expose command is given to the controller, the camerais already receiving the signal on the "green" line from the adapter.Therefore, an internal expose command is sent from the adapter to thecamera to initiate an exposure cycle in the camera which records theimage at position 2 on the film and sets the next exposure to made atposition 3.

Subsequent actuation of the expose command of the adapter will causeexposures to be made at the subsequent positions on the film. After animage is recorded at position 6 the film is used up and the camerasignals the operator to change film. After insertion of new film thecamera sends a ready signal to the adapter and the system is now readyto start exposing another film in either color or black-and-white.

It should be noted, as mentioned above, that the conventionalblack-and-white multi-image camera may not be designed and constructedto hold sets of image locations in positions 1 through 6 on the film tothe closer positional tolerances that are required to achieve adequateregistration of the three color image components in the viewer describedherein. Accordingly, image position adjustment may be necessary in theviewer as the record image components fixed on the film cannot be moved.Such adjustments may be made either manually or by a viewer withautomatic convergence control as described above.

Rotating Lens Board

As set forth above, the adapter of FIG. 17 is programmed to cause theconventional camera (in color mode) to expose image components in asequence (Col. 1, Row 1; Col. 1, Row 2; Col. 1, Row 3; Col. 2, Row 1;Col. 2, Row 2; Col. 2, Row 3) different than the black-and-whitestandard sequence (Col. 1, Row 1; Col. 2, Row 1; Col. 1, Row 2; Col. 2,Row 2; Col. 1, Row 3; Col. 2, Row 3) that is normally followed by theconventional camera. However, it may not be desirable or feasible tomodify exposure sequence of certain conventional cameras. Therefore, inorder to allow the conventional camera to expose image components in thesame normal or standard sequence of positions for both black-and-whiteand color mode, the viewer may be modified as shown in FIGS. 19 and 20(sheet 11). FIG. 18 shows a standard sheet of film 379 having two setsof color image components R1, B1, G1 for a first image and G2, B2, R2for a second image. These components are positioned on film sheet 379 inthe positions and sequence controlled by a standard camera following itsstandard sequence of black-and-white exposure positions. Thus, insequence, the standard camera exposes the three components R1, B1, G1 ofthe first image in first, second and third positions of its standardsequencing and, continuing its standard sequencing for the second image,sequentially exposes components G2, B2, R2 in the standard fourth, fifthand sixth positions, as illustrated in FIG. 18. This color componentsequence (R,B,G,G,B,R) is different than the color component sequenceemployed in embodiments described above, but requires only a change inthe sequencing of the adapter multiplexer.

For viewing of image components arranged in positions shown in FIG. 18,the viewer is modified as shown in FIGS. 19 and 20. This viewerconfiguration enables viewing of two full images, namely all six colorimage components, on a sheet film with but three projection lenses. Forviewing a film record having color image components of two images ofwhich components are arranged as illustrated in FIG. 18, threeprojection lenses are mounted on a rigid lens board 380 (FIG. 19) thatpivots about an axis 381. Lenses 382, 383, and 384 are mounted on theboard in the angulated or inverted L-shaped configuration illustrated inFIG. 19. These lenses are in positions 1,2 and 3, Col. 1, Row 1; Col. 2,Row 1; and Col. 1, Row 2, with the board 380 oriented as shown in FIG.19. These lenses are provided with three separate light sources, threeseparate condenser lenses and three separate light path isolationtunnels formed by the series of baffle plates, all described inconnection with FIGS. 6 and 7. A second set of three lenses, such as thesecond set of FIGS. 6 and 7, namely lenses 132A, 134A, and 136A,together with the related structures are not employed in the arrangementof FIGS. 19 and 20.

In the arrangement of FIGS. 19 and 20 the green lens 384 is fixedlymounted on the board and in a position corresponding to image positionthree (G1 in FIG. 18) of the film, whereas red and blue lenses 382 and383 are mounted on the board in positions corresponding to positions R1and B1 of the film of FIG. 18. If deemed necessary or desirable the redand blue lenses as previously described may be mounted to the board onmovable stages for X and Y adjustment to enable registration in precisesuperposition of the three superposed projected images. Thus, the red,blue and green lenses are mounted in positions geometrically congruentwith the first three standard positions on the film, so that thecomponents of the first image may all be projected in superposition onthe screen by means of lenses 382,383,384.

To enable viewing of the second image (components G2, B2, R2 in standardpositions 4, 5 and 6) with this viewer and film configuration, the lensboard is rotated 180° about axis 381 to position the lenses asillustrated in FIG. 20. In this position the respective green, blue andred lenses 384, 383 and 382 are in positions congruent with the filmpositions 4, 5 and 6 of image components G2, B2 and R2 of FIG. 18.

The embodiment illustrated in FIGS. 18 through 20 enables use of aviewer with fewer components and permits standard camera sequencing. Nochange in black-and-white exposure sequencing of the standard camera isneeded.

In use of this viewer for viewing two different images on a filmconfigured and arranged as illustrated in FIG. 18 the first image isviewed with the rotatably adjustable lens board 380 in the positionillustrated in FIG. 19 whereas for viewing the second image lens boardis rotated to the position illustrated in FIG. 20. If motors are used toadjust the movable stages of the "red" and "blue" lens positionsrelative to the fixed "green" lens, the motors may be part of a closedloop automatic image registration (automatic convergence) system asdescribed above. The movable stages have to move in opposite directionsin the two positions of the lens board to properly control imageregistration. This is achieved by changing polarity of the motor drivesignals when the lens board is rotated from one position to the other.

Staggered Lens Viewer

In another modification of the described system, as shown in FIGS.21-27, improved physical size and layout of the lenses are provided andthe viewer has only one group of three lenses arranged in staggeredrelation. These lenses are provided with three separate light sources,three separate condenser lenses and three separate light path isolationtunnels formed by the series of baffle plates, all as described inconnection with FIGS. 6 and 7. The second set of three lenses of FIGS. 6and 7, namely lenses 132A, 134A, and 136A, together with the relatedstructures are not employed in the arrangement of FIGS. 21-27. Toutilize such a viewer, having only three lenses, the film record sheetis recorded with a single appropriately positioned group of three colorimage components. However, two such groups may also be employed,provided that the respective color image components of each image arepositioned as illustrated in FIG. 21 (sheet 10). Each of the two colorimages formed on a film sheet 370, includes three separate color imagecomponents designated B1, G1, R1 and R2, G2, B2, respectively in FIG.21. To be capable of use with a viewer having but three lenses, thecomponents of the first image are respectively, positioned on film sheet370, in a staggered relation. Thus, components of the first image asshown in FIG. 21 are positioned on film 370 with the blue component B1of the first image in the upper left corner (Col. 1, Row 1), the greencomponent G1 of the first image in the center of the right side (Col. 2,Row 2) and the red component R1 of the first image in the lower leftcorner (Col. 1, Row 3). The components of the second image of the twoimages formed on the standard 8×10 inch film are also positioned asillustrated in FIG. 21, with the red component R2 of the second image inthe upper right corner (Col. 2, Row 1), the green component G2 of thesecond image in the center of the left side (Col. 1, Row 2) and the bluecomponent B2 of the second image positioned in the lower right corner(Col. 2, Row 3) of the film. The several image components have uniqueorientations, as illustrated in FIG. 23 (sheet 12) and as will bedescribed below.

In a camera arranged to expose image components in the arrangement ofFIG. 21, the monochrome images representing the individual color imagecomponents are first electronically formed, in sequence, on the face ofthe CRT, as previously described and then optically distributed, byappropriate sequential operation of the lens shutters, to be projectedto six different positions on the film through the six different cameralenses 60, 62, 64 and 60a, 62a, 64a. The lenses of the modified viewerare positioned with respect to the various image components of the twoimages of sheet film 370 as illustrated in FIG. 27 (sheet 12).

The camera configuration for providing the image component distributionof FIG. 21 is the same as that previously described and illustrated inFIGS. 2, 3, 4 and 5, but with the deflection controls of the cathode raytube modified to enable reversal of the deflection signals to obtainselected image component orientations. Thus, as shown in FIG. 22 (sheet10), the signal from a horizontal deflection drive 371 for the CRT 50 isfed through 2 poles of a 4-pole, double throw relay 372a, having A and Bpositions, to the horizontal deflection coils 373, 374 of the cathoderay tube. Similarly, vertical deflection signals from a verticaldeflection driver 375 of the cathode ray tube are fed through the other2 poles of the 4-pole, double throw relay 372b, having positions A andB, to vertical deflection coils 377, 378 of the cathode ray tube. Thearrangement enables selectively turning the recorded images upside downand from right to left by reversing polarity of the current to thedeflection yoke coils. The displayed raster can be scanned on the CRTface either from top to bottom or from bottom to top in the verticaldirection, and either from left to right or right to left in thehorizontal direction. If the vertical direction of scan and thehorizontal direction of scan are both reversed the effect is to turn theimage upside down. As a practical matter, the polarity of the sweepcurrents cannot be switched instantaneously, because the high energy ofthe sweep would result in arcing at the relay contacts that would causethem to deteriorate. It is necessary to turn off the sweeps beforeswitching and turn them back on after switching. Since the switching isdone between images, this is not a difficulty. An alternative is to dothe switching electronically. These details, which use standardtechniques, are not shown.

Sets of image components are positioned on the record film 370 in thesix positions illustrated in FIGS. 21 and 23. Also illustrated in FIG.23 are the unique orientations of the individual image components. Thus,the components of the first image, that is, components B1, G1, and R1,as shown in FIG. 23, are positioned right side up (as indicated by thearrows), but are reversed from right to left (as indicated by lines witha circle on one end), whereas the components R2, G2, B2 of the secondimage, as shown in FIG. 23, are positioned normally from right to left,but are all upside down. In the image orientation convention usedherein, the arrows point to the top of the image and the circle is atthe right side of the image. These orientations enable simplifiedviewing of both sets of images with a viewer having but three lenses aswill be described below. With the film record components positioned andoriented as illustrated in FIG. 23 the viewer arrangement illustrated inFIG. 2 (to be described below) will provide a composite projected firstimage oriented as indicated at 380 in FIG. 24. This projected image hasnormal orientation in both up and down directions and from right toleft.

For use with a record having the component arrangement of FIG. 23, theviewer lenses are configured in a staggered arrangement similar to thestaggered arrangement of the image components of one image of the film.The staggered arrangement of the three viewer lenses includes a blueprojection lens 394 (FIG. 27) positioned toward an upper left side ofthe group as viewed in the direction looking from the lenses toward thescreen. This corresponds to Col. 1, Row 1 of the record array. A greenprojection lens 395 is positioned at an intermediate right section (Col.2, Row 2) of the lens group and a red projection lens 396 is positionedat a lower left portion (Col. 1, Row 3) of the group. The blue, greenand red viewer lenses are positioned to project light passing throughthree image components in positions B1, G1, and R1 of film 370. FIG. 27illustrates the relative position of the components of the first imageon film 370 with respect to the three projection lenses 394, 395, 396,with the film 370 oriented for projection of the first image (componentsB1, G1, R1). In this arrangement condenser lenses 390, 391 and 392 are,as previously described, positioned in the same staggered arrangementimmediately adjacent the respective staggered film image components andsymmetrically arranged with respect to the associated film imagecomponents. Orientation of the projected first image when the film 370is positioned in the viewer in the orientation shown in FIGS. 23 and 27,as previously described, the normal orientation is shown in FIG. 24.

The camera configuration employed for making the record shown in FIG. 21is the same as that previously illustrated. It has an optical systemwith lenses that operate with an object outside their focal points andwith a single mirror. Therefore, the lenses invert the images left toright and top to bottom and the mirror reverses the images again, top tobottom only. Orientation of the color image components of the firstimage as shown in FIG. 23 is accomplished by sweeping the CRT scanbottom to top vertically and left to right horizontally. Assume thiscorresponds to position A of the relay 372 of FIG. 22. To obtain theorientation of color image components of the second image as shown inFIG. 25 the relay is switched to position B to change the sweepdirections to top to bottom vertically and right to left horizontally,which turns the images upside down with respect to the components of thefirst image.

Employing the previously described camera with the deflection reversingrelay illustrated, in FIG. 22, the three-component electronic colorimage is spatially encoded on the record film in the positions assignedto the first image as illustrated in FIG. 23, by the following sequenceof steps controlled by the camera microprocessor.

A) Place the sweep reversing relay in position A.

B) Open the shutter of the lens in the red position (lens 64, Col. 1,Row 3 of FIG. 21).

C) Select the red component electronic image via the multiplexer anddirect it to the monitor. Unblank the CRT to display the image. Afterthe proper exposure time (typically one second) blank the CRT.

D) Close the shutter of the lens in the red position and open theshutter of the lens in the green position (lens 62a, Col. 2, Row 2 ofFIG. 21).

E) Select the green component electronic image and direct it to themonitor. Unblank the CRT, displaying the green image component. Afterthe proper exposure time blank the CRT.

F) Close the shutter of the lens in the green position and open theshutter of the lens in the blue position (lens 60, Col. 1, Row 1).

G) Select the blue component electronic image and direct it to themonitor. Unblank the CRT displaying the blue image component. After theproper exposure time blank the CRT.

H) Close the shutter of the lens in the blue position.

The three image components of the first image have now been exposed onthe film.

With the camera in its color mode and when a film holder is firstinserted into the camera the camera controller sets the state of thecamera to record a color image in the manner described above, recordingcolor image components R1, G1, and B1. If the film holder is not removedthe controller thereafter sets its state to record the next color imageas a second color image with the following sequence of steps.

I) Put the sweep reversing relay into position B.

J) Open the shutter of the lens in the red position (lens 60a, Col. 2,Row 1 of FIG. 21).

K) Select the red component electronic image and direct it to themonitor. Unblank the CRT, displaying the image. After proper exposuretime blank the CRT.

L) Close the shutter of the lens in the red position and open theshutter of the lens (62) in the green position (Col. 1, Row 2).

M) Select the green component electronic image, direct it to themonitor, unblank the CRT to display the image and blank the CRT afterthe proper exposure time.

N) Close the shutter of lens in the green position and open the shutterof the lens 64a in the blue position (Col. 2, Row 3) for this image.

O) Select the blue component electronic image, direct it to the monitor,unblank the CRT and display the image. Blank the CRT again after theproper exposure time.

P) Close the shutter of the lens in the blue position.

The three image components of the second image have now been exposed.

With the camera in its black-and-white mode, instead of the justdescribed color mode, the sweep reversing relay remains in the Aposition at all times so that all six images on the film have the sameorientation, which is the orientation shown in FIG. 23 for the firstimage. This orientation, with the film emulsion side up has the imagescorrect top to bottom but all reversed left to right. To view theblack-and-white images in correct orientation on a conventional lightbox the film is turned over side to side (e.g. rotated about an axislying in the film plane and extending from top to bottom of the film) sothat its emulsion side is down. This is the normal way of viewingblack-and-white films in order to protect the emulsion surface. Now theimages are correctly oriented both top to bottom and left to right.

In the black-and-white mode of the camera, when the film holder is firstinserted into the camera, the camera controller will set the camerastate so that the first image is placed in the upper right corner (Col.2, Row 1) of the film, looking at the film with emulsion side up. Thisis done so that this image component will be in the upper left corner(Col. 1, Row 1) when the film is turned over. After the first image isrecorded the next active image position is in the upper left corner(Col. 1, Row 1). The active image positions then progress right to leftand top to bottom until six positions are filled. The film holder thenis removed from the camera. The electronic image signal comes into thecamera on the green multiplexer channel and is permanently selected inthis black-and-white mode to send the signal to the monitor. For eachimage of the six black-and-white images the sequence is as followings.

Q) Open the shutter of the lens corresponding to the first active image(Col. 2, Row 1) position.

R) Unblank the CRT displaying the image and then blank the CRT after theproper exposure time.

S) Close the shutter.

T) Advance to the next active image position (Col. 1, Row 1).

Repeat for the remaining positions.

It will be understood that the common exposure control calibration maybe carried out before each exposure of the camera in conventionalfashion so as to maintain constant exposure parameters on the film.

As previously mentioned the viewer employed for the described staggeredimage component film configuration of FIG. 21 is substantially the sameas that previously described in FIGS. 6, 7, 8, 9, 10 and 11, except forthe fact that there are only three light sources, three condenser lensesand three projection lenses. Positions of the projection lenses and thecondenser lenses are illustrated in FIG. 27 which is a top view of theviewer. In this view the projection lenses 394,395,396 are above thefilm and the condenser lenses 390,391,392 are beneath the film.

For color projection by the modified viewer of FIG. 27 to view spatiallyencoded color images on black-and-white film having two sets of recordedimage color components arranged as illustrated in FIG. 23, the film isplaced in the film drawer and the drawer closed, to position the filmimage components in the optical projection path. For viewing of a firstcolor image (B1,G1,R1), the film is positioned in the drawer in theorientation relative to the lenses as illustrated in FIG. 27. The threecolor record image components are projected in mutual superposition onthe viewer's projection screen, the red component with red light, thegreen component with green light and the blue component with blue light.The color image components of the second image are not projected on thescreen because there are no light sources or projection lenses in linewith these components.

The projection lenses of the viewer in the arrangement illustrated inFIG. 27, reverse the film images both left to right and top to bottom,and the single mirror in the optical path of the viewer (mirror 142,FIG. 6) reverses the images top to bottom again. The resultant compositecolor projection of the first image therefore appears on the viewer'sscreen oriented as illustrated in FIG. 24 which is correct left to rightand top to bottom.

To view the second color image the film is withdrawn from the viewer andturned end for end in a horizontal plane. That is, it is rotated 180°about an axis perpendicular to the film plane. The film is thenpositioned in the film drawer in the orientation illustrated in FIG. 25.Now, the three color record image components B2, G2,R2 of the secondimage (in Col. 1, Row 1; Col. 2, Row 2; and Col. 1, Row 3) are in theoptical projection paths of the three lenses (which are fixed in theviewer at Col. 1, Row 1; Col. 2, Row 2; and Col. 1, Row 3). Since thesecolor record image components are upside down on the film, as comparedto the color image components of the first image, and are similarlysymmetrically placed, the color record images of the second image arenow properly positioned and properly oriented to be projected on thescreen and to appear on the screen as a composite color image properlyoriented as shown in FIG. 26 which has correct left to right and top tobottom orientations.

The lenses of the staggered arrangement of FIG. 27 also may be arrangedfor X,Y adjustment of the "red" and "blue" lenses relative to the"green" lens, either manually or automatically, as described inconnection with the other viewer lens arrangements discussed above.

A number of advantages result from the described modified viewer andstaggered image component arrangements on the record film. The staggeredconfiguration of the projection lenses of the viewer (as shown in FIG.27), enables the lenses to be placed farther apart (with a given lenspackage boundary area). In other words, the lenses can be at a greatercenter to center distance, permitting projection lenses of largerdiameter to be used. The resulting larger lens apertures result in amore efficient optical projection system, requiring light sources oflower power for the same screen brightness and reducing heat dissipationand cooling problems. The larger lens barrel diameters also permitdesign of projection lenses with less off axis vignetting which yieldsprojected images of more uniform luminance and less color shading.

Another advantage is that the staggered positions of the three filmimages that make up a single image allow use of three condenser lenseswhich are round instead of rectangular. The staggered lens positioningavoids mechanical interference of the round condenser lenses with oneanother as is the case if six condenser lenses instead of three arerequired and if staggering of condenser lenses is not possible withinthe same physical envelope. This round configuration of condenser lenseswithout mechanical interference is illustrated in FIG. 27. Round lensesare less expensive in moderate quantities than rectangular lenses whichmust be either cut down from round lenses or specially molded.

Yet another advantage is that the viewer is mechanically less complexand contains fewer components than other configurations, making it bothless expensive and more reliable. There is no need for mechanicalmovement of the film inside the viewer or any need of mechanical motionof the lenses to project the second image of a film sheet. Nor is thereany need for the added complexity of switching of multiple lightsources.

Although the several systems described herein all use three separatecolors to form a single full color image, it will be understood thatprinciples of the invention may be applied by using other numbers ofseparate colors (or other colors), such as, for example, two separatecolors, or four separate colors. For example, the viewer may projectlight of different spectral content in its several paths. Blue, greenand red light beams are generally in the range of 4-500, 5-600 and 6-700micrometers, respectively, but other spectral ranges and contents andother numbers of separate image components may be employed.

There have been described systems and methods for color imaging,particularly useful for images initially embodied in electrical colorcomponent signals, and particularly useful for medical diagnosticimaging using standard black-and-white sheet film and processing systemsand providing color records having all of the advantages ofblack-and-white film records.

I claim:
 1. A color imaging system for use with a plurality ofelectrical signals respectively representing different monochromaticcolor components of a subject, said imaging system comprising:a piece ofmonochromatic film, camera means responsive to said signals for formingon said monochromatic film a plurality of mutually spaced monochromaticimage components respectively representing said different monochromaticcolor components, means for processing said film to fix saidmonochromatic image components thereon, and viewer means having a screenand including means for projecting images of said fixed monochromaticfilm image components on said screen in mutual superposition and eachwith a different spectral content, whereby projected monochromaticimages of different spectral content are combined on the screen to forma single multi-color image of the subject.
 2. The system of claim 1wherein said camera means comprise a monochromatic cathode ray tube,means for sequentially feeding said signals to said tube, film holdermeans mounted adjacent said tube for holding said piece of monochromaticfilm, lens means mounted between said tube and film holder means forprojecting light from said tube to form said image components uponmutually spaced areas of said monochromatic film.
 3. The system of claim1 wherein said film comprises a single sheet of standard 8×10 inchmonochromatic film, said mutually spaced monochromatic image componentsbeing formed on said sheet of film.
 4. The system of claim 1 whereinsaid viewer means comprises a light source, a viewer film holderinterposed between said screen and light source and configured andarranged to hold said piece of film with said mutually spacedmonochromatic image components at mutually spaced image projection areasof the viewer means, said means for projecting comprising projectionlens means interposed between said viewer film holder and said screenfor providing a plurality of optical projection paths from said lightsource through respective ones of said areas to a common region of saidscreen, and means in respective ones of said optical paths for impartingindividually different colors to light in respective ones of said paths,whereby color image components on a piece of film in said viewer filmholder may be projected in mutual superposition on said common region.5. The system of claim 1 wherein said viewer means comprise a housing,said means for projecting including projection lens means in saidhousing comprising a first lens mounted to said housing and having aprojection axis, and second and third lenses, means for mounting each ofsaid second and third lenses for adjustable displacement relative tosaid first lens in a plane substantially perpendicular to the axis ofsaid first lens, whereby misregistration of superposition of images onsaid screen may be minimized by displacement of said first and secondlens.
 6. The system of claim 1 wherein said viewer means include ahousing, said means for projecting including projection lens means insaid housing comprising a plurality of lenses having nominal relativepositions for providing a plurality of optical paths that converge onsaid screen, and means for adjusting said lenses to vary the convergenceof said optical paths.
 7. The system of claim 6 wherein said means foradjusting comprises a manually operable mechanism.
 8. The system ofclaim 6 wherein said means for adjusting comprises means forautomatically varying said convergence.
 9. The system of claim 8 whereineach of said film image components includes reference indicia, andwherein said means for automatically varying comprises a sensor, meansfor projecting said indicia on said sensor, and means responsive to saidsensor for moving said lenses.
 10. The system of claim 1 wherein saidcamera means includes an optical system having a first magnification,said means for projecting including a projection lens system having asecond magnification that is substantially the reciprocal of said firstmagnification.
 11. The system of claim 1 wherein said color componentsare three in number, and wherein said camera means includes means forforming on said monochromatic film three reference spots, each spotbeing associated with an individual one of said monochromatic imagecomponents on said film and having a predetermined position with respectto such associated image component, said means for projecting comprisingfirst, second and third lens means for providing three mutuallyconverging optical paths to said screen through respective ones of saidfixed monochromatic film image components, said viewer including opticalsensor means positioned adjacent said screen, said lens means beingconfigured and arranged to project images of said three reference spotsof said fixed film along converging optical paths to said sensor, andmeans responsive to said sensor for adjusting relative positions of saidlens means to enhance convergence of said projected spots on saidsensor.
 12. The system of claim 1 wherein said camera means includesmeans for forming reference spots on said film in predetermined relationto respective ones of said monochromatic image components, said viewermeans including a sensor positioned adjacent said screen, said viewerincluding a plurality of lens means for projecting images of saidreference spots of said monochromatic film image components on saidsensor in nominal mutual superposition with a predetermined nominalmisregistration, and means responsive to said sensor for adjustingrelative positions of said lens means to decrease misregistration ofsaid projected images of said reference spots.
 13. The system of claim12 wherein said lens means includes first, second and third lenses, andwherein said means for adjusting said lens means comprise means formounting said first and second lenses for adjustment with respect tosaid third lens, and means responsive to said sensor for automaticallyadjusting said first and second lenses relative to said third lens so asto decrease actual misregistration of the projected image of saidsuperposed reference spots.
 14. A medical diagnostic color imagingsystem for use with a medical diagnostic scanning device that providesan output having a plurality of electrical signals respectivelyrepresenting different color image components of a subject scanned bysaid device, said system comprising:input means for providing electricalsignals representing different color image components of a subjectscanned by said device, a film holder configured and arranged to hold apiece of monochromatic film, and means responsive to said input meansfor exposing a plurality of record image components on different areasof a piece of film in said holder, each of said record image componentscomprising a record image of a different one of said signal components.15. The system of claim 14 wherein said input means comprises a memoryfor storing at least one frame of each of said signal components, andwherein said means for exposing comprises a multiplexer responsive tosaid memory, and a cathode ray tube responsive to said multiplexer. 16.A method of medical diagnostic color imaging for use with a medicaldiagnostic color scanning device that provides an electrical outputhaving electrical signals respectively representing different colorimage components of a subject that is scanned by the device, said methodcomprising the steps of:employing the output of said scanning device toform on a piece of monochromatic film a plurality of mutually spacedmonochromatic image components that respectively represent saiddifferent color image components, processing the film to fix themonochromatic image components thereon, and forming on a viewing mediuma plurality of mutually superposed projected images of saidmonochromatic image components of said processed film, said step offorming comprising projecting each of said images with a differentspectral content so as to combine the projected monochromatic images ofdifferent spectral content on the viewing medium to form a singlemulti-color image of the scanned subject.
 17. The method of claim 16wherein said step of projecting comprises the step of superposing saidimages on said viewing medium with a mutual registration error that isnot greater than an error that causes a visibly discerniblemisregistration of the superposed images component.
 18. The method ofclaim 16 wherein said step of projecting comprises superposition of saidimages on said viewing medium so that the deviation of the registrationof at least one of said projected images with respect to another is notgreater than about 0.020 inches.
 19. A viewing system for displayingcolor images comprising:a piece of film having a set of monochromaticimage components thereon, said film having a plurality of mutuallyspaced image areas in an array of areas having columns 1 and 2 and rows1, 2 and 3, said set of image components comprising image componentsrepresenting three different colors that collectively define a firstimage, the components of said set being positioned on said film in areasthereof identified respectively as column 1, row 1, column 2, row 2, andcolumn 1 row
 3. 20. The system of claim 19 including a second set ofimage components on said film comprising image components representingthree different colors that collectively define a second image, thecomponents of said second set being positioned on said film in areasthereof identified respectively as column 2, row 3, column 1, row 2 andcolumn 2, row
 1. 21. The system of claim 20 including viewer means forprojecting image components of one of said sets of monochromatic imagecomponents of said film in mutually registered superposition to providea full color image of said first image, said viewer means comprising alight source, a screen, film holder means for holding said film betweensaid screen and light source, projection lens means interposed betweensaid film holder means and said screen for providing three convergingoptical projection paths from said light source through respective onesof said image components of said one set to converge on a common regionof said screen, image components of said film being projected in mutualsuperposition on said common region, said projection lens meansincluding first, second and third lenses positioned in column 1, row 1,column 2, row 2 and column 1, row 3 respectively of an imaginary lensarray having columns 1 and 2 and rows 1, 2, and 3, said viewer meansincluding means in respective ones of said optical paths for impartingindividually different colors to light in respective ones of said paths.22. The system of claim 21 wherein orientations of the image componentsof said second set are reversed from right to left and from top tobottom with respect to the orientations of the image components of saidfirst mentioned set, whereby said film may be positioned in a firstorientation in said viewer for projection of image components of saidfirst mentioned set and may be positioned in said viewer in a secondorientation that is rotated relative to said first orientation 180°about an axis perpendicular to the plane of the film for projection ofimage components of said second set through said lenses.
 23. An opticalfilm record for storing first and second color images comprising:a sheetof monochromatic film having first and second sets of image componentsarranged in an array of image components, said array including columns 1and 2 and rows 1, 2 and 3 of image components, said first set of imagecomponents comprising first, second and third monochromatic imagecomponents respectively representing first, second and third colorcomponents of a first image, said second set of image componentscomprising first, second and third monochromatic components respectivelyrepresenting first, second and third color components of a second image,whereby said sheet of monochromatic film stores image components of twocolor images.
 24. The film record of claim 23 wherein the components ofsaid first set are positioned respectively in column 1 row 1, column 2row 2 and column 1 row 3 of said array.
 25. The film record of claim 23wherein the image components of said first set are all positioned incolumn 1 and the image components of said second set are all positionedin column 2 of said array.
 26. The film record of claim 23 wherein theimage components of said first set are positioned respectively in column1 row 1, column 2 row 2 and column 1 row 3, and wherein the componentsof said second image are positioned respectively in column 2 row 3,column 1 row 2 and column 2 row
 1. 27. The film record of claim 23wherein the image components of said first image are positionedrespectively in column 1 row 1, column 2 row 1, and column 1 row 2, andwherein the image components of second image are positioned respectivelyin column 2 row 2, column 2 row 3 and column 1 row
 3. 28. A coloradapter for a monochromatic camera having a monochromatic cathode raytube, means for feeding electrical signals representing an image of anobject to be recorded to said cathode ray tube, a film holder forholding a piece of monochromatic film, and shuttered lens means forselectively exposing on different areas of said film images presented onsaid cathode ray tube at selectively different times, said adaptercomprising:means for providing first, second and third color componentelectrical signals collectively representing a color image of an object,means for sequentially transmitting said color component signals to saidcathode ray tube, and means synchronized with the transmitting of saidsignals to said cathode ray tube for sequentially exposing mutuallyseparate areas of said film to said cathode ray tube to create on saidmonochromatic film separate image components of the respective colorimage component signals.
 29. The adapter of claim 28 wherein said meansfor sequentially exposing comprises means for locating said imagecomponents in column 1, row 1, column 2, row 2, column 1, row 3 of anarray of positions on said film having columns 1 and 2 and rows 1, 2 and3.
 30. The adapter of claim 28 wherein said means for sequentiallyexposing comprises means for locating said image components in column 1,row 1, column 2, row 1 and column 1, row 2 of an array of positions onsaid film having columns 1 and 2 and rows 1, 2 and
 3. 31. A colorimaging system comprising:a monochromatic camera including:amonochromatic cathode ray tube, means for feeding electrical signalsrepresenting an image of an object to be recorded to said cathode raytube, a film holder for holding a piece of monochromatic film, andshuttered lens means for selectively exposing on different areas of saidfilm an image presented on said cathode ray tube at selectivelydifferent times, and adapter means for causing the camera to expose onsaid film a plurality of image components respectively representingdifferent monochromatic color components of a subject, said adaptercomprising:means for providing a plurality of color component electricalsignals collectively representing a color image of an object, means forsequentially transmitting said color component signals to said cathoderay tube, and means synchronized with the transmitting of said signalsto said cathode ray tube for sequentially exposing mutually separateareas of said film to said cathode ray tube to create on saidmonochromatic film separate image components of the respective colorimage component signals.
 32. A method of color imaging a subjectrepresented by a plurality of electrical signals respectivelyrepresenting different monochromatic color components of said subject,said method comprising:employing said signals to form on a piece ofmonochromatic film a plurality of mutually spaced monochromatic imagecomponents respectively representing said different monochromaticcomponents, processing said film to fix said monochromatic imagecomponents thereon, and projecting images of said fixed monochromaticfilm image components on a display medium in mutual superposition andeach with a different spectral content, whereby projected monochromaticimages of different spectral content are combined on the display mediumto form a single multi-color image of the subject.
 33. A viewer forprojecting a color image of an object represented by a set ofmonochromatic image components on a piece of film, said viewercomprising:a light source, a screen, a film holder, a plurality ofprojection lenses interposed between said screen and film holder, saidlenses being positioned in a lens plane containing an imaginary array oflens areas arranged in columns 1 and 2 and rows 1, 2 and 3, said lensesbeing positioned in said plane at areas thereof respectively identifiedas column 1, row 1, column 2, row 2, and column 1, row 3, and means forimparting different spectral characteristics to light passing throughrespective ones of said lenses.
 34. The viewer of claim 33 wherein saidlast mentioned means comprises different color filters.
 35. A viewer forprojecting a color image of an object represented by a set ofmonochromatic image components on a piece of film, said viewercomprising:a light source, a screen, a film holder, a plurality ofprojection lenses interposed between said screen and film holder, saidlenses being positioned in a lens plane and being positioned in amutually staggered relation in said plane, whereby center to centerdistance between said lenses is increased for a given lens packageboundary area, said lenses being mounted in a lens package having apredetermined boundary area, and means for imparting different spectralcharacteristics to light passing through respective ones of said lenses.36. A viewing system for displaying color images comprising:a piece offilm having a set of monochromatic image components thereon, said filmhaving a plurality of mutually spaced image areas in an array of areashaving columns 1 and 2 and rows 1, 2 and 3, said set of image componentscomprising image components representing three different colors thatcollectively define a first image, components of said first set beingpositioned on said film in areas identified respectively as column 1,row 1, column 2, row 1 and column 1, row 2 said film having a second setof image components positioned on said film in areas identifiedrespectively as column 2, row 1, column 2, row 3 and column 1, row 3,and a viewer including,a lens board movable between first and secondpositions, first, second and third lenses having projecting axes andbeing mounted, in said first position of said lens board, in arraypositions corresponding to column 1, row 1, column 2, row 1 and columnrow 2, respectively, of said array, and means for mounting said lensboard for rotation about an axis that is substantially parallel to theaxes of said lenses between said first position and said secondposition, said second position being turned 180° with respect to saidfirst position, whereby the image components of said first set may beprojected by said lenses when said lens board is in said first positionand the image components of said second set on said film may beprojected by said lenses when said lens board is in said secondposition.
 37. A viewer comprising:projection means including a lensboard having a first first, second and third lenses on said lens boardhaving projection axes and positioned in column 1, row 1, column 2, row2 and column 1, row 3 respectively of an imaginary lens array havingcolumns 1 and 2 and rows 1, 2 and 3, when said lens board is in saidfirst position, and means for mounting said lens board for rotationabout an axis that is parallel to the axes of said lenses from saidfirst position to a second position that is turned 180° with respect tosaid first position.
 38. A method of forming an optical color record ofan object comprising the steps of:providing monochromatic signalsrespectively representing different color components of an image of saidobject, employing said signals to produce on a common piece ofmonochromatic film mutually separated monochromatic images ofrespectively different ones of said color components with a firstpredetermined nominal relative positioning, wherein the maximumdeviation of actual relative positioning of any two of saidmonochromatic images from said nominal relative positioning is notgreater than a deviation that would cause a visibly discernablemisregistration of said color components when said monochromatic imagesare displayed upon a viewing screen in mutual superposition by a viewerconstructed and arranged to provide a mutually superposed displaywithout visibly discernable misregistration of images having saidnominal predetermined relative positioning.
 39. The method of claim 38wherein said maximum deviation is not greater than about 0.012 inches.40. A method of forming an optical color record of an object, whereinthe record comprises a plurality of monochromatic record images that arearranged to be displayed upon a viewing screen by a viewer that displaysin mutual superposition and without visibly discernable misregistrationa plurality of record images having a predetermined nominal relativepositioning, said method comprising the steps of:providing threemonochromatic signals respectively representing three different colorcomponents of an image of said object, employing said signals to produceon a common piece of monochromatic film a plurality of mutuallyseparated monochromatic record images of respective ones of said colorcomponents with an actual relative positioning, wherein the maximumdeviation of said actual relative positioning of any two of saidmonochromatic images from said nominal relative positioning is notgreater than a deviation that would cause a visibly discernablemisregistration of said color components when said monochromatic imagesare displayed by said viewer.
 41. The method of claim 40 wherein saidmaximum deviation is not greater than about 0.012 inches.
 42. A methodof displaying a color image of an object comprising the stepsof:providing on a common piece of monochromatic film a plurality ofmutually separated monochromatic images of respective ones of differentcolor components of said object, and displaying said monochromaticimages in mutual superposition upon a viewing screen with a deviation ofpositioning of any two of said monochromatic images from a precisemutual registration that is not greater than a deviation that causes avisibly discernable misregistration of said two monochromatic images onsaid viewing screen.
 43. The method of claim 42 wherein said step offorming separated images comprises positioning two of said monochromaticimages on said film with a deviation of relative positioning from apredetermined relative positioning of not more than about 0.012 inches.44. The method of claim 42 wherein said step of displaying comprisesadjusting position of at least one of said monochromatic images on saidscreen relative to position of another one of said monochromatic imageson said screen.
 45. The method of claim 44 wherein said step ofadjusting is performed manually.
 46. The method of claim 44 wherein saidstep of adjusting is performed automatically.
 47. The method of claim 42wherein said step of providing comprises providing said separated imageon a single sheet of standard black-and-white film.
 48. An optical colorrecord for use with a viewer that displays in mutual superposition andwithout visibly discernable misregistration three record images having apredetermined nominal relative positioning, said optical recordcomprising:a sheet of monochromatic film, and three mutually separaterecord images formed on said film, said images respectively representingindividual ones of three color components of an object, at least two ofsaid images having an actual relative positioning that deviates from anominal relative positioning by a maximum deviation that would cause avisibly discernable misregistration when said images are displayed inmutual superposition by said viewer.
 49. The color record of claim 48wherein said sheet of monochromatic film comprises a standard sheet of8×10 inch black-and-white film.
 50. The optical color record of claim 48wherein said maximum deviation is about 0.012 inches.
 51. A viewer fordisplaying a color image comprising:a light source, a screen, a filmholder interposed between said screen and light source and configuredand arranged to hold a film record having a plurality of mutually spacedmonochromatic images at three mutually spaced image areas, projectionlens means interposed between said film holder and said screen forproviding a plurality of optical paths from said source throughrespective ones of said areas to a common region of said screen, wherebymonochromatic images formed on a sheet of film in said holder andrespectively representing components of different spectral content of anobject image may be projected in mutual superposition on said commonregion, and means in respective ones of said optical paths for impartingindividually different spectral content to light in respective ones ofsaid paths.
 52. The viewer of claim 51 wherein said light sourcecomprises three separate light sources each generating light of anindividually different color, said light sources comprising said meansfor imparting different colors to light in said paths.
 53. The viewer ofclaim 51 wherein said projection lens means comprises first, second andthird lenses lying in a common plane generally perpendicular to at leastone of said optical paths, and means for adjustably moving said secondand third lenses relative to said first lens in first and secondmutually transverse directions in said common plane, whereby projectionson said screen of each of said second and third ones of saidmonochromatic images may be adjustably moved into precise registrationwith the projection of said screen of a third one of said monochromaticimages.
 54. The viewer of claim 53 wherein said film holder comprises aframe mounted for motion between a loading position displaced from saidoptical paths and a viewing position in said optical paths, said framecomprising a plurality of film support members collectively definingthree film holder openings that form said mutually spaced image areas,said support members including vacuum means for securing a sheet of filmto said frame.
 55. The viewer of claim 53 including baffle means betweensaid film holder and said lenses for mutually isolating said opticalpaths.
 56. The viewer of claim 54 wherein said frame comprises aslidable drawer having frame members configured and arranged to hold astandard sheet of 8×10 inch black-and-white film.
 57. The viewer ofclaim 53 including a lens mount, said second and third lenses beingmounted in said lens mount for separate motion in said transversedirections, said first lens being fixed to said lens mount, and firstand second manually operable adjusting means for separately andindividually moving said second and third lenses relative to said firstlens so as to obtain precise registration of all superposed images onsaid screen.
 58. The viewer of claim 56 including means responsive tomotion of said frame to said viewing position for activating said vacuummeans and said light source.
 59. A camera for forming a color record ofan object comprising:a housing, means in said housing for providingthree signals respectively representing three different monochromaticcolor components of an image of said object, a monochromatic cathode raytube in said housing, means in said housing for sequentially feedingsaid signals to said tube, film holder means in said housing for holdinga piece of monochromatic film, first, second and third lens meansmounted in said housing between said tube and film holder means forrespectively projecting first, second and third record images of saidtube upon three mutually separate areas of film in said holdermeans,said first and second lens means being positioned relative to saidthird lens means to cause said first and second record images to havepositions that deviate from nominal positions of said first and secondrecord images relative to the position of said third image by adeviation not greater than a maximum deviation that would cause avisibly discernable misregistration of said color components when saidrecord images are displayed upon a screen in mutual superposition by aviewer constructed and arranged to provide a mutually superposed displaywithout visibly discernable misregistration of record images having saidnominal positions, and normally closed shutter means in said housingbetween said lens means and said film holder for selectively passinglight from respective ones of said lens means in synchronism with thesequential feeding of said signals to said tube.
 60. The camera of claim59 wherein said maximum deviation is not greater than about 0.012inches.
 61. In combination, a camera for forming a color record of anobject, and a viewer for displaying said color record, said cameracomprising:a housing, means for providing a plurality of signalsrespectively representing three different monochromatic color componentsof an image of said object, a monochromatic cathode ray tube in saidhousing, means in said housing for sequentially feeding said signals tosaid tube, film holder means in said housing for holding a piece ofmonochromatic film, camera lens means mounted in said housing betweensaid tube and film holder means for projecting light from said tube toform a plurality of color record image components upon mutually spacedareas of a piece of monochromatic film in said holder means, normallyclosed shutter means in said housing between said lens means and saidfilm holder means for selectively passing light from said lens means inaccordance with the sequential feeding of said signals to said tube,said viewer comprising: a light source, a screen, a viewer film holderinterposed between said screen and light source and configured andarranged to hold a piece of film having mutually spaced color recordimage components at mutually spaced image ares thereof, projection lensmeans interposed between said viewer film holder and said screen forproviding a plurality of converging optical paths from said light sourcethrough respective ones of said areas to a common region of said screen,whereby color record image components formed on a piece of film in saidviewer film holder and respectively representing different color imagecomponents of an object image may be projected in mutual superpositionon said common region, and means in respective ones of said opticalpaths for imparting individually different spectral characteristics tolight in respective ones of said paths.
 62. The combination of claim 61wherein said film holder means of said camera are configured andarranged to hold a sheet of monochromatic 8×10 inch film.
 63. Thecombination of claim 61 wherein said camera lens means has a firstmagnification and wherein said projection lens means has a secondmagnification that is the reciprocal of said first magnification.